



Internet Engineering Task Force (IETF)                        Q. Ma, Ed.
Request for Comments: 9922                                         Q. Wu
Category: Standards Track                                         Huawei
ISSN: 2070-1721                                        M. Boucadair, Ed.
                                                                  Orange
                                                                 D. King
                                                    Lancaster University
                                                              March 2026


                A Common YANG Data Model for Scheduling

Abstract

   This document defines common types and groupings that are meant to be
   used for scheduling purposes, such as events, policies, services, or
   resources based on date and time.  For the sake of better modularity,
   the YANG module includes a set of recurrence-related groupings with
   varying levels of representation (i.e., from basic to advanced) to
   accommodate a variety of requirements.  It also defines groupings for
   validating requested schedules and reporting scheduling statuses.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   https://www.rfc-editor.org/info/rfc9922.

Copyright Notice

   Copyright (c) 2026 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   Trust Legal Provisions and are provided without warranty as described
   in the Revised BSD License.

Table of Contents

   1.  Introduction
   2.  Conventions and Definitions
   3.  Module Overview
     3.1.  Features
     3.2.  Types and Identities
     3.3.  Scheduling Groupings
       3.3.1.  The "generic-schedule-params" Grouping
       3.3.2.  The "period-of-time" Grouping
       3.3.3.  The "recurrence-basic" Grouping
       3.3.4.  The "recurrence-utc" Grouping
       3.3.5.  The "recurrence-with-time-zone" Grouping
       3.3.6.  The "recurrence-utc-with-periods" Grouping
       3.3.7.  The "recurrence-time-zone-with-periods" Grouping
       3.3.8.  The "icalendar-recurrence" Grouping
       3.3.9.  The "schedule-status",
               "schedule-status-with-time-zone", and
               "schedule-status-with-name" Groupings
     3.4.  Features Use and Augmentations
   4.  Some Usage Restrictions
   5.  Relationship to the DISMAN-SCHEDULE-MIB
   6.  The "ietf-schedule" YANG Module
   7.  Security Considerations
   8.  IANA Considerations
     8.1.  The IETF XML Registry
     8.2.  The YANG Module Names Registry
   9.  References
     9.1.  Normative References
     9.2.  Informative References
   Appendix A.  Examples of Scheduling Format Representation
     A.1.  The "generic-schedule-params" Grouping
     A.2.  The "period-of-time" Grouping
     A.3.  The "recurrence-basic" Grouping
     A.4.  The "recurrence-utc" Grouping
     A.5.  The "recurrence-with-time-zone" Grouping
     A.6.  The "recurrence-utc-with-periods" Grouping
     A.7.  The "recurrence-time-zone-with-periods" Grouping
     A.8.  The "icalendar-recurrence" Grouping
     A.9.  The "schedule-status" Grouping
   Appendix B.  Examples of Using/Extending the "ietf-schedule" Module
     B.1.  Example: Schedule Tasks to Execute Based on a Recurrence
           Rule
     B.2.  Example: Schedule Network Properties to Change Based on
           Date and Time
   Appendix C.  Examples of Using the "ietf-schedule" Module for
           Scheduled Use of Resources Framework
   Acknowledgments
   Authors' Addresses

1.  Introduction

   This document defines a common schedule YANG module ("ietf-schedule")
   that can be used in several scheduling contexts, e.g., (but not
   limited to) [YANG-NAC], [YANG-OAM], and [YANG-SCHEDULE].  The module
   includes a set of reusable groupings that are designed to be
   applicable for scheduling purposes, such as events, policies,
   services, or resources based on date and time.  It also defines
   groupings for validating requested schedules and reporting scheduling
   statuses.

   This document does not make any assumption about the nature of
   actions that are triggered by the schedules.  Detection and
   resolution of any schedule conflicts are beyond the scope of this
   document.

   Section 5 discusses the relationship with the Management Information
   Base (MIB) managed objects for scheduling management operations
   defined in [RFC3231].

   Appendix A describes a set of examples to illustrate the use of the
   common schedule groupings (Section 3.3).  Appendix B provides sample
   modules to exemplify how future modules can use the extensibility
   provisions in the "ietf-schedule" module (Section 6).  Also,
   Appendix C provides an example of using the "ietf-schedule" module
   for scheduled use of a resources framework (e.g., [RFC8413]).

2.  Conventions and Definitions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

   The meanings of the symbols in tree diagrams are defined in
   [RFC8340].

   This document uses the YANG terminology defined in Section 3 of
   [RFC7950].

   This document makes use of the following terms:

   Recurrence rule:  Refers to a rule or repeating pattern for recurring
      events.  See also Section 3.8.5.3 of [RFC5545] for a comprehensive
      iCalendar recurrence rule specification.

   Recurrence instance (or Recurrence, for short):  Refers to an
      instance that matches a recurrence rule.

   Recurrence set:  Refers to a set of recurrence instances.

   Frequency:  Characterizes the type of a recurrence rule.  Values are
      taken from the "FREQ" rule in Section 3.3.10 of [RFC5545].

      For example, repeating events based on an interval of a second or
      more are classified as recurrence with a frequency value of
      "SECONDLY".  Frequency values defined as identities in the YANG
      module are used in lowercase.

   iCalendar:  Refers to Internet Calendaring per [RFC5545].

   Interval:  Refers to an integer that specifies the interval at which
      a recurrence rule repeats.  Values are taken from the "INTERVAL"
      rule in Section 3.3.10 of [RFC5545].

      For example, "1" means every second for a secondly rule, every
      minute for a minutely rule, every hour for an hourly rule, etc.

   System:  Refers to an entity that hosts a schedule that is managed
      using the YANG module defined in this document.

   "schedule-status-*" refers to any of "schedule-status", "schedule-
   status-with-time-zone", and "schedule-status-with-name".

3.  Module Overview

3.1.  Features

   The "ietf-schedule" data model defines the recurrence-related
   groupings using a modular approach.  To that aim, a variety of
   representations of recurrence groupings ranging from basic to
   advanced (iCalender-like) are defined.  To allow for different
   options, two features are defined in the data model:

   *  "basic-recurrence"

   *  "icalendar-recurrence"

   Refer to Section 3.4 and Appendix B.1 for the use of these features.

3.2.  Types and Identities

   The "ietf-schedule" module (Section 6) defines the following
   identities:

   *  "schedule-type": Indicates the type of schedule.  The following
      types are defined so far:

      -  one-shot: This type is used for a schedule that triggers an
         action that has either the duration specified as 0 or the end
         time specified as the same as the start time, and then the
         schedule will disable itself (Section 3.3 of [RFC3231]).

      -  period: This type is used for a period-based schedule
         consisting of either (1) a start and end or (2) a start and
         positive duration of time.  If neither an end nor a duration is
         indicated, the period is considered to last forever.

      -  recurrence: This type is used for a recurrence-based schedule.
         A recurrence may be periodic (i.e., repeat over the same
         period, e.g., every five minutes) or not (i.e., repeat in a
         non-regular manner, e.g., every day at 8 and 9 AM).

   *  "frequency-type": Characterizes the repeating interval rule of a
      recurrence schedule (secondly, minutely, etc.).

   *  "schedule-state": Indicates the status of a schedule (enabled,
      disabled, conflicted, finished, etc.).  This identity can also be
      used to manage the state of individual instances of a recurrence-
      based schedule.

   *  "discard-action-type": Specifies the action for the responder to
      take (e.g., generate a warning or an error message) when a
      requested schedule cannot be accepted for any reason and is
      discarded.

3.3.  Scheduling Groupings

   The "ietf-schedule" module (Section 6) defines the following
   groupings:

   *  "generic-schedule-params" (Section 3.3.1)

   *  "period-of-time" (Section 3.3.2)

   *  "recurrence-basic" (Section 3.3.3)

   *  "recurrence-utc" (Section 3.3.4)

   *  "recurrence-with-time-zone" (Section 3.3.5)

   *  "recurrence-utc-with-periods" (Section 3.3.6)

   *  "recurrence-time-zone-with-periods" (Section 3.3.7)

   *  "icalendar-recurrence" (Section 3.3.8)

   *  "schedule-status", "schedule-status-with-time-zone", and
      "schedule-status-with-name" (Section 3.3.9)

   Examples are provided in Appendix A.

3.3.1.  The "generic-schedule-params" Grouping

   A system accepts and handles schedule requests, which may help
   further automate the scheduling process of events, policies,
   services, or resources based on date and time.  The "generic-
   schedule-params" grouping (Figure 1) specifies a set of configuration
   parameters that are used by a system for validating requested
   schedules.

     grouping generic-schedule-params:
       +-- description?            string
       +-- time-zone-identifier?   sys:timezone-name
       +-- validity?               yang:date-and-time
       +-- max-allowed-start?      yang:date-and-time
       +-- min-allowed-start?      yang:date-and-time
       +-- max-allowed-end?        yang:date-and-time
       +-- discard-action?         identityref

        Figure 1: 'generic-schedule-params' Grouping Tree Structure

   The "description" parameter includes a description of the schedule.
   No constraint is imposed on the structure nor the use of this
   parameter.

   The "time-zone-identifier" parameter, if provided, specifies the time
   zone reference [RFC7317] of the local date and time values.  This
   parameter MUST be specified if any of the date and time values are in
   the format of local time.  It MUST NOT be applied to date and time
   values that are specified in the format of UTC or time zone offset to
   UTC.

   The "validity" parameter specifies the date and time after which a
   schedule will not be considered as valid.  It determines the latest
   time that a schedule can be started and thus executed independently
   from when it ends, and it takes precedence over similar attributes
   that are provided at the schedule instance itself.  A requested
   schedule may still be accepted, but any occurrences that start later
   than the configured value will not be executed.

   The "max/min-allowed-start" parameters specify the maximum/minimum
   scheduled start date and time.  A requested schedule will be rejected
   if the first occurrence of the schedule starts later/earlier than the
   configured values.

   The "max-allowed-end" parameter specifies the maximum allowed end
   time of the last occurrence.  A requested schedule will be rejected
   if the end time of the last occurrence is later than the configured
   "max-allowed-end" value.

   The "discard-action" parameter specifies the action if a requested
   schedule cannot be accepted for any reason and is discarded.
   Possible reasons include, but are not limited to, the requested
   schedule failing to satisfy the guards in this grouping, conflicting
   with existing schedules, or being out-of-date (e.g., the expected
   start has already passed).

   These parameters apply to all schedules on a system and are meant to
   provide guards against stale configuration, schedule requests that
   are too short and that would thus prevent validation by admins of
   some critical systems, etc.

3.3.2.  The "period-of-time" Grouping

   The "period-of-time" grouping (Figure 2) represents a time period
   using either a start date and time ("period-start") and end date and
   time ("period-end") or a start date and time ("period-start") and a
   non-negative time duration ("duration").  For the first format, the
   start of the period MUST be no later than the end of the period.  If
   neither an end date and time ("period-end") nor a duration
   ("duration") is indicated, the period is considered to last forever.
   If the duration ("duration") value is 0 or the end time ("period-
   end") is the same as the start time ("period-start"), the period is
   considered as a one-shot schedule.  If no start date and time
   ("period-start") is specified, the period is considered to start
   immediately.

   The "time-zone-identifier" parameter indicates the identifier for the
   time zone.  This parameter MUST be specified if either the "period-
   start" or "period-end" value is reported in local time format.  It
   MUST NOT be applied to date and time values that are specified in the
   format of UTC or time zone offset to UTC.

   The "period-description" parameter includes a description of the
   period.  No constraint is imposed on the structure nor the use of
   this parameter.

     grouping period-of-time:
       +-- period-description?     string
       +-- period-start?           yang:date-and-time
       +-- time-zone-identifier?   sys:timezone-name
       +-- (period-type)?
          +--:(explicit)
          |  +-- period-end?       yang:date-and-time
          +--:(duration)
             +-- duration?         duration

             Figure 2: 'period-of-time' Grouping Tree Structure

3.3.3.  The "recurrence-basic" Grouping

   The "recurrence-basic" grouping (Figure 3) specifies a simple
   recurrence rule that starts immediately and repeats forever.

     grouping recurrence-basic:
       +-- recurrence-description?   string
       +-- frequency?                identityref
       +-- interval?                 uint32

            Figure 3: 'recurrence-basic' Grouping Tree Structure

   The frequency parameter ("frequency") identifies the type of
   recurrence rule.  For example, a "daily" frequency value specifies
   repeating events based on an interval of a day or more.

   Consistent with Section 3.3.10 of [RFC5545], the interval parameter
   ("interval") represents at which interval the recurrence rule
   repeats.  For example, within a "daily" recurrence rule, an interval
   value of "8" means every eight days.

   Note that, per Section 4.13 of [YANG-GUIDE], no "default"
   substatement is defined here for both "frequency" and "interval"
   parameters because there are cases (e.g., profiling) where using
   these statements is problematic.  No "mandatory" substatement is
   defined here for the same reason.  YANG modules using this grouping
   SHOULD refine these two nodes with either a "mandatory" or a
   "default" statement if they always need to be configured or have
   default values.  This recommendation MAY be ignored in cases such as
   when this grouping is used by another grouping.

   The "recurrence-description" parameter includes a description of the
   period.  No constraint is imposed on the structure nor the use of
   this parameter.

3.3.4.  The "recurrence-utc" Grouping

   The "recurrence-utc" grouping (Figure 4) uses the "recurrence-basic"
   grouping (Section 3.3.3) and specifies a simple recurrence rule in
   UTC format.

     grouping recurrence-utc:
       +-- recurrence-first
       |  +-- start-time-utc?   yang:date-and-time
       |  +-- duration?         uint32
       +-- (recurrence-end)?
       |  +--:(until)
       |  |  +-- utc-until?          yang:date-and-time
       |  +--:(count)
       |     +-- count?              uint32
       +-- recurrence-description?   string
       +-- frequency?                identityref
       +-- interval?                 uint32

             Figure 4: 'recurrence-utc' Grouping Tree Structure

   The "start-time-utc" parameter indicates the start time in UTC
   format.

   The "duration" parameter specifies, in units of seconds, the time
   period of the first occurrence.  Unless specified otherwise (e.g.,
   through additional augmented parameters), the "duration" also applies
   to subsequent recurrence instances.  When unspecified, each
   occurrence is considered as immediate completion (e.g., execute an
   immediate command that is considered to complete quickly) or hard to
   compute an exact duration (e.g., run a data analysis script whose
   execution time may depend on the data volume and computation resource
   availability).  The behavior to follow when a task takes more time
   than specified by the "duration" is out of scope.  Such
   considerations belong to task management, not schedule management.

   Note that the "interval" and "duration" cover two distinct properties
   of a schedule event.  The interval specifies when a schedule will
   occur, combined with the frequency parameter, while the duration
   indicates how long an occurrence will last.  This document allows the
   interval between occurrences to be shorter than the duration of each
   occurrence (e.g., a recurring event is scheduled to start every day
   for a duration of 2 days).

   The repetition can be scoped by a specified end time or by a count of
   occurrences, indicated by the "recurrence-end" choice.  The "count"
   value MUST be greater than 1, and the "start-time-utc" value always
   counts as the first occurrence.

   The "recurrence-utc" grouping is designed to be reused in scheduling
   contexts where machine readability is more desirable.

3.3.5.  The "recurrence-with-time-zone" Grouping

   The "recurrence-with-time-zone" grouping (Figure 5) uses the
   "recurrence-basic" grouping (Section 3.3.3) and specifies a simple
   recurrence rule with a time zone.

     grouping recurrence-with-time-zone:
       +-- recurrence-first
       |  +-- start-time?   yang:date-and-time
       |  +-- duration?     duration
       +-- time-zone-identifier?     sys:timezone-name
       +-- (recurrence-end)?
       |  +--:(until)
       |  |  +-- until?              yang:date-and-time
       |  +--:(count)
       |     +-- count?              uint32
       +-- recurrence-description?   string
       +-- frequency?                identityref
       +-- interval?                 uint32

       Figure 5: 'recurrence-with-time-zone' Grouping Tree Structure

   The "recurrence-first" container includes "start-time" and "duration"
   parameters to specify the start time and period of the first
   occurrence.  Unless specified otherwise (e.g., through additional
   augmented parameters), the "duration" also applies to subsequent
   recurrence instances.  When unspecified, each occurrence is
   considered as immediate completion (e.g., execute an immediate
   command that is considered to complete quickly) or hard to compute an
   exact duration (e.g., run a data analysis script whose execution time
   may depend on the data volume and computation resource availability).

   The grouping also includes a "time-zone-identifier" parameter, which
   MUST be specified if either the "start-time" or "until" value is
   reported in local time format.  It MUST NOT be applied to date and
   time values that are specified in the format of UTC or time zone
   offset to UTC.

   The repetition can be scoped by a specified end time or by a count of
   occurrences, indicated by the "recurrence-end" choice.  The "count"
   value MUST be greater than 1, and the "start-time" value always
   counts as the first occurrence.

   The considerations discussed in Section 3.3.4 for "interval" and
   "duration" are also applicable to "recurrence-with-time-zone".

   Unlike the definition of the "recurrence-utc" grouping
   (Section 3.3.4), "recurrence-with-time-zone" is intended to promote
   human readability over machine readability.

3.3.6.  The "recurrence-utc-with-periods" Grouping

   The "recurrence-utc-with-periods" grouping (Figure 6) uses the
   "recurrence-utc" grouping (Section 3.3.4) and adds a "period-
   timeticks" list to define an aggregate set of repeating occurrences.

     grouping recurrence-utc-with-periods:
       +-- recurrence-first
       |  +-- start-time-utc?   yang:date-and-time
       |  +-- duration?         uint32
       +-- (recurrence-end)?
       |  +--:(until)
       |  |  +-- utc-until?          yang:date-and-time
       |  +--:(count)
       |     +-- count?              uint32
       +-- recurrence-description?   string
       +-- frequency?                identityref
       +-- interval?                 uint32
       +-- period-timeticks* [period-start]
          +-- period-start    yang:timeticks
          +-- period-end?     yang:timeticks

      Figure 6: 'recurrence-utc-with-periods' Grouping Tree Structure

   The recurrence instances are specified by the union of occurrences
   defined by both the recurrence rule and "period-timeticks" list.
   This list uses the "yang:timeticks" type defined in [RFC9911].
   Duplicate instances are ignored.  The value of the "period-start"
   instance MUST NOT exceed the value of the "frequency" instance, i.e.,
   the "timeticks" value must not exceed 100 in a secondly recurrence
   rule, and it must not exceed 6000 in a minutely recurrence rule, and
   so on.

3.3.7.  The "recurrence-time-zone-with-periods" Grouping

   The "recurrence-time-zone-with-periods" grouping (Figure 7) uses the
   "recurrence-with-time-zone" grouping (Section 3.3.5) and adds a
   "period" list to define an aggregate set of repeating occurrences.

     grouping recurrence-time-zone-with-periods:
       +-- recurrence-first
       |  +-- start-time?   yang:date-and-time
       |  +-- duration?     duration
       +-- time-zone-identifier?     sys:timezone-name
       +-- (recurrence-end)?
       |  +--:(until)
       |  |  +-- until?              yang:date-and-time
       |  +--:(count)
       |     +-- count?              uint32
       +-- recurrence-description?   string
       +-- frequency?                identityref
       +-- interval?                 uint32
       +-- period* [period-start]
          +-- period-description?     string
          +-- period-start            yang:date-and-time
          +-- time-zone-identifier?   sys:timezone-name
          +-- (period-type)?
             +--:(explicit)
             |  +-- period-end?       yang:date-and-time
             +--:(duration)
                +-- duration?         duration

   Figure 7: 'recurrence-time-zone-with-periods' Grouping Tree Structure

   The recurrence instances are specified by the union of occurrences
   defined by both the recurrence rule and "period" list.  Duplicate
   instances are ignored.

3.3.8.  The "icalendar-recurrence" Grouping

   The "icalendar-recurrence" grouping (Figure 8) uses the "recurrence-
   time-zone-with-periods" grouping (Section 3.3.7) and defines more
   data nodes to enrich the definition of recurrence.  The structure of
   the "icalendar-recurrence" grouping refers to the definition of the
   recurrence component defined in Sections 3.3.10 and 3.8.5 of
   [RFC5545].

     grouping icalendar-recurrence:
       +-- recurrence-first
       |  +-- start-time?   yang:date-and-time
       |  +-- duration?     duration
       +-- time-zone-identifier?     sys:timezone-name
       +-- (recurrence-end)?
       |  +--:(until)
       |  |  +-- until?              yang:date-and-time
       |  +--:(count)
       |     +-- count?              uint32
       +-- recurrence-description?   string
       +-- frequency?                identityref
       +-- interval?                 uint32
       +-- period* [period-start]
       |  +-- period-description?     string
       |  +-- period-start            yang:date-and-time
       |  +-- time-zone-identifier?   sys:timezone-name
       |  +-- (period-type)?
       |     +--:(explicit)
       |     |  +-- period-end?       yang:date-and-time
       |     +--:(duration)
       |        +-- duration?         duration
       +-- bysecond*                 uint32
       +-- byminute*                 uint32
       +-- byhour*                   uint32
       +-- byday* [weekday]
       |  +-- direction*   int32
       |  +-- weekday      schedule:weekday
       +-- bymonthday*               int32
       +-- byyearday*                int32
       +-- byyearweek*               int32
       +-- byyearmonth*              uint32
       +-- bysetpos*                 int32
       +-- workweek-start?           schedule:weekday
       +-- exception-dates*          yang:date-and-time

          Figure 8: 'icalendar-recurrence' Grouping Tree Structure

   An array of the "bysecond" (or "byminute" or "byhour") specifies a
   list of seconds within a minute (or minutes within an hour or hours
   of the day).  For example, within a "minutely" recurrence rule, the
   values of "byminute" node "10" and "20" mean the occurrences are
   generated at the 10th and 20th minute within an hour, reducing the
   number of recurrence instances from all minutes.

   The parameter "byday" specifies a list of days of the week, with an
   optional direction that indicates the nth occurrence of a specific
   day within the "monthly" or "yearly" frequency instance.  Valid
   values of "direction" are 1 to 5 or -5 to -1 within a "monthly"
   recurrence rule and 1 to 53 or -53 to -1 within a "yearly" recurrence
   rule.  For example, within a "monthly" rule, the "weekday" with a
   value of "monday" and the "direction" with a value of "-1" represents
   the last Monday of the month.

   An array of the "bymonthday" (or byyearday", "byyearweek", or
   "byyearmonth") specifies a list of days of the month (or days of the
   year, weeks of the year, or months of the year).  For example, within
   a "yearly" recurrence rule, the values of "byyearmonth" instances "1"
   and "2" mean the occurrences are generated in January and February,
   increasing the "yearly" recurrence from every year to every January
   and February of the year.

   The "bysetpos" conveys a list of values that corresponds to the nth
   occurrence within the set of recurrence instances to be specified.
   For example, in a "monthly" recurrence rule, the "byday" data node
   specifies every Monday of the week, and the "bysetpos" with a value
   of "-1" represents the last Monday of the month.  Not setting the
   "bysetpos" data node represents every Monday of the month.

   The "workweek-start" data node specifies the day on which the week
   starts.  This is significant when a "weekly" recurrence rule has an
   interval greater than 1, and a "byday" data node is specified.  This
   is also significant when in a "yearly" rule and a "byyearweek" is
   specified.  Note that, per Section 4.13 of [YANG-GUIDE], no "default"
   substatement is defined here because there are cases (e.g.,
   profiling) where using these statements is problematic.  No
   "mandatory" substatement is defined here for the same reason.  YANG
   modules using this grouping SHOULD refine the "workweek-start" node
   with either a "mandatory" or a "default" statement if it always needs
   to be configured or has a default value.  This MAY be ignored in
   cases such as when this grouping is used by another grouping.

   The "exception-dates" data node specifies a list of exceptions for
   recurrence.  The final recurrence set is generated by gathering all
   of the date and time values created by any of the specified
   recurrence rules and date-times and then excluding any start date and
   time values specified by "exception-dates" parameter.

3.3.9.  The "schedule-status", "schedule-status-with-time-zone", and
        "schedule-status-with-name" Groupings

   The "schedule-status", "schedule-status-with-time-zone", and
   "schedule-status-with-name" groupings (Figure 9) define common
   parameters for scheduling management/status exposure.  The "schedule-
   status-with-time-zone" grouping has the same structure as "schedule-
   status" but with an additional parameter to identify a time zone.
   Similarly, the "schedule-status-with-name" grouping has the same
   structure as "schedule-status" but with an additional parameter to
   identify a schedule "schedule-name".  These structures are defined in
   the module to allow for better modularity and flexibility.

     grouping schedule-status:
       +-- state?                    identityref
       +-- version?                  uint16
       +-- schedule-type?            identityref
       +--ro local-time?               yang:date-and-time
       +--ro last-update?              yang:date-and-time
       +--ro counter?                  yang:counter32
       +--ro last-occurrence?          yang:date-and-time
       +--ro upcoming-occurrence?      yang:date-and-time
       +--ro last-failed-occurrence?   yang:date-and-time
       +--ro failure-counter?          yang:counter32
     grouping schedule-status-with-time-zone:
       +--ro time-zone-identifier?  sys:timezone-name
       +-- schedule-name?            string
       +-- state?                    identityref
       +-- version?                  uint16
       +-- schedule-type?            identityref
       +--ro local-time?               yang:date-and-time
       +--ro last-update?              yang:date-and-time
       +--ro counter?                  yang:counter32
       +--ro last-occurrence?          yang:date-and-time
       +--ro upcoming-occurrence?      yang:date-and-time
       +--ro last-failed-occurrence?   yang:date-and-time
       +--ro failure-counter?          yang:counter32
     grouping schedule-status-with-name:
       +-- schedule-name?            string
       +-- state?                    identityref
       +-- version?                  uint16
       +-- schedule-type?            identityref
       +--ro local-time?               yang:date-and-time
       +--ro last-update?              yang:date-and-time
       +--ro counter?                  yang:counter32
       +--ro last-occurrence?          yang:date-and-time
       +--ro upcoming-occurrence?      yang:date-and-time
       +--ro last-failed-occurrence?   yang:date-and-time
       +--ro failure-counter?          yang:counter32

           Figure 9: 'schedule-status-*' Groupings Tree Structure

   The "schedule-name" parameter is useful to uniquely identify a
   schedule in a network device or controller if multiple scheduling
   contexts exist.

   The "state" parameter is defined to configure/expose the scheduling
   state, depending on the use of the grouping.  For a recurrence-based
   schedule, it represents the state of the overall recurrence.  The
   "identityref" type is used for this parameter to allow extensibility
   in future modules.

   The "version" parameter is used to track the current schedule version
   information.  The version can be incremented by the entity that
   created the schedule.  The "last-update" parameter identifies when
   the schedule was last modified.  In some contexts, this parameter can
   be used to track the configuration of a given schedule.  In such
   cases, the "version" may not be used.

   The "schedule-type" parameter identifies the type of the current
   schedule.  The "counter", "last-occurrence", and "upcoming-
   occurrence" data nodes are only available when the "schedule-type" is
   "recurrence".

   When no time zone is included, "local-time" reports the actual local
   time as seen by the entity that hosts a schedule.  This parameter can
   be used by a controller to infer the offset to UTC.  This use is
   similar to the use of "schedLocalTime" in [RFC3231].

   "last-failed-occurrence" and "failure-counter" report the last
   failure that occurred and the count of failures for this schedule.
   Unless new parameters/operations are defined to allow the count of
   failures to be reset, "failure-counter" is reset by default only when
   the schedule starts.

   The current groupings capture common parameters that are applicable
   to typical scheduling contexts known so far.  Future modules can
   define other useful parameters as needed.  For example, in a
   scheduling context with multiple system sources to feed the
   schedules, the "source" and "precedence" parameters may be needed to
   reflect how schedules from different sources should be prioritized.

3.4.  Features Use and Augmentations

   Appendix B.1 provides an example about how the features defined in
   Section 3.1 can be used.  Implementations may support a basic
   recurrence rule or an advanced one, as needed, by declaring different
   features.  Whether only one or both features are supported is
   implementation specific and depends on the specific scheduling
   context.

   The common schedule groupings (Section 3.3) can also be augmented to
   support specific needs.  As an example, Appendix B.2 demonstrates how
   additional parameters can be added to comply with specific schedule
   needs.

4.  Some Usage Restrictions

   There are some restrictions that need to be followed when using
   groupings defined in the "ietf-schedule" YANG module (Section 3.3):

   *  The instant in time represented by "period-start" MUST be before
      the "period-end" for the "period-of-time" grouping
      (Section 3.3.2).

   *  The combination of the day, month, and year represented for date
      and time values MUST be valid.  See Section 5.7 of [RFC3339] for
      the maximum day number based on the month and year.

   *  Unless deployed in contexts where time synchronization is not
      subject to leap second adjustments (e.g., Section 4.3 of [NTPv5]),
      the second for date and time values SHOULD have the value "60" at
      the end of months in which a leap second occurs.

   *  Schedules received with a starting time in the past with respect
      to current time SHOULD be ignored.  When a local policy is
      provided, an implementation MAY omit the past occurrences and
      start immediately (e.g., for a period-based schedule) or start
      from the date and time when the recurrence pattern is first
      satisfied from the current time (e.g., for a recurrence-based
      schedule).

5.  Relationship to the DISMAN-SCHEDULE-MIB

   [RFC3231] specifies a Management Information Base (MIB) used to
   schedule management operations periodically or at specified dates and
   times.

   Although no data nodes are defined in this document, Table 1 lists
   how the main objects in the DISMAN-SCHEDULE-MIB can be mapped to YANG
   parameters.

              +==================+=========================+
              | MIB Object       | YANG                    |
              +==================+=========================+
              | schedLocalTime   | local-time              |
              +------------------+-------------------------+
              | schedType        | schedule-type           |
              +------------------+-------------------------+
              | schedName        | schedule-name           |
              +------------------+-------------------------+
              | schedOwner       | Not Supported           |
              +------------------+-------------------------+
              | schedDescr       | description             |
              +------------------+-------------------------+
              | schedInterval    | interval                |
              +------------------+-------------------------+
              | schedWeekDay     | weekday                 |
              +------------------+-------------------------+
              | schedMonth       | byyearmonth             |
              +------------------+-------------------------+
              | schedDay         | bymonthday              |
              +------------------+-------------------------+
              | schedHour        | byhour                  |
              +------------------+-------------------------+
              | schedMinute      | byminute                |
              +------------------+-------------------------+
              | schedContextName | Not Supported           |
              +------------------+-------------------------+
              | schedAdminStatus | state                   |
              +------------------+-------------------------+
              | schedOperStatus  | state                   |
              +------------------+-------------------------+
              | schedFailures    | failure-counter         |
              +------------------+-------------------------+
              | schedLastFailure | Not Supported           |
              +------------------+-------------------------+
              | schedLastFailed  | last-failed-occurrence  |
              +------------------+-------------------------+
              | schedStorageType | Not Supported           |
              +------------------+-------------------------+
              | schedVariable    | Not applicable          |
              +------------------+-------------------------+
              | schedValue       | Not applicable          |
              +------------------+-------------------------+
              | schedTriggers    | counter/failure-counter |
              +------------------+-------------------------+

                        Table 1: YANG/MIB Mapping

6.  The "ietf-schedule" YANG Module

   This module imports types defined in [RFC9911] and [RFC7317].

   <CODE BEGINS>
   file "ietf-schedule@2026-03-10.yang"
   module ietf-schedule {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:yang:ietf-schedule";
     prefix schedule;

     import ietf-yang-types {
       prefix yang;
       reference
         "RFC 9911: Common YANG Data Types";
     }

     import ietf-system {
       prefix sys;
       reference
         "RFC 7317: A YANG Data Model for System Management";
     }

     organization
       "IETF NETMOD Working Group";
     contact
       "WG Web:  <https://datatracker.ietf.org/wg/netmod/>
        WG List: <mailto:netmod@ietf.org>

        Editor:   Qiufang Ma
                  <mailto:maqiufang1@huawei.com>
        Author:   Qin Wu
                  <mailto:bill.wu@huawei.com>
        Editor:   Mohamed Boucadair
                  <mailto:mohamed.boucadair@orange.com>
        Author:   Daniel King
                  <mailto:d.king@lancaster.ac.uk>";
     description
       "This YANG module defines a set of common types and groupings
        that are applicable for scheduling purposes, such as events,
        policies, services, or resources based on date and time.

        The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL
        NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'NOT RECOMMENDED',
        'MAY', and 'OPTIONAL' in this document are to be interpreted as
        described in BCP 14 (RFC 2119) (RFC 8174) when, and only when,
        they appear in all capitals, as shown here.

        Copyright (c) 2026 IETF Trust and the persons identified
        as authors of the code.  All rights reserved.

        Redistribution and use in source and binary forms, with
        or without modification, is permitted pursuant to, and
        subject to the license terms contained in, the Revised
        BSD License set forth in Section 4.c of the IETF Trust's
        Legal Provisions Relating to IETF Documents
        (https://trustee.ietf.org/license-info).

        This version of this YANG module is part of RFC 9922; see
        the RFC itself for full legal notices.

        All revisions of IETF and IANA-maintained modules can be found
        in the 'YANG Parameters' registry group
        (https://www.iana.org/assignments/yang-parameters).";

     revision 2026-03-10 {
       description
         "Initial revision.";
       reference
         "RFC 9922: A Common YANG Data Model for Scheduling";
     }

     feature basic-recurrence {
       description
         "Indicates that the server supports configuring a basic
          scheduled recurrence.";
     }

     feature icalendar-recurrence {
       description
         "Indicates that the server supports configuring a comprehensive
          scheduled iCalendar recurrence.";
       reference
         "RFC 5545: Internet Calendaring and Scheduling Core Object
                    Specification (iCalendar),
                    Sections 3.3.10 and 3.8.5";
     }

     typedef weekday {
       type enumeration {
         enum sunday {
           value 0;
           description
             "Sunday of the week.";
         }
         enum monday {
           value 1;
           description
             "Monday of the week.";
         }
         enum tuesday {
           value 2;
           description
             "Tuesday of the week.";
         }
         enum wednesday {
           value 3;
           description
             "Wednesday of the week.";
         }
         enum thursday {
           value 4;
           description
             "Thursday of the week.";
         }
         enum friday {
           value 5;
           description
             "Friday of the week.";
         }
         enum saturday {
           value 6;
           description
             "Saturday of the week.";
         }
       }
       description
         "Seven days of the week.";
     }

     typedef duration {
       type string {
         pattern '((\+)?|\-)P((([0-9]+)D)?(T(0[0-9]|1[0-9]|2[0-3])'
               + ':[0-5][0-9]:[0-5][0-9]))|P([0-9]+)W';
       }
       description
         "Duration of the time.  The format can represent nominal
          durations (weeks designated by 'W' and days designated by 'D')
          and accurate durations (hours:minutes:seconds follows the
          designator 'T').

          Note that this value type doesn't support the 'Y' and 'M'
          designators to specify durations in terms of years and months.

          Negative durations are typically used to schedule an alarm to
          trigger before an associated time.";
       reference
         "RFC 5545: Internet Calendaring and Scheduling Core Object
                    Specification (iCalendar), Sections 3.3.6 and
                    3.8.6.3";
     }

     identity schedule-type {
       description
         "Base identity for schedule type.";
     }

     identity one-shot {
       base schedule-type;
       description
         "Indicates a one-shot schedule.  That is a schedule that
          will trigger an action with the duration being specified as
          0 or end time being specified as the same as the start time,
          and then the schedule will disable itself.";
     }

     identity period {
       base schedule-type;
       description
         "Indicates a period-based schedule consisting of either a
          start and end or a start and positive duration of time.  If
          neither an end nor a duration is indicated, the period is
          considered to last forever.";
     }

     identity recurrence {
       base schedule-type;
       description
         "Indicates a recurrence-based schedule.";
     }

     identity frequency-type {
       description
         "Base identity for frequency type.";
     }

     identity secondly {
       base frequency-type;
       description
         "Indicates a repeating rule based on an interval of
          a second or more.";
     }

     identity minutely {
       base frequency-type;
       description
         "Indicates a repeating rule based on an interval of
          a minute or more.";
     }

     identity hourly {
       base frequency-type;
       description
         "Indicates a repeating rule based on an interval of
          an hour or more.";
     }

     identity daily {
       base frequency-type;
       description
         "Indicates a repeating rule based on an interval of
          a day or more.";
     }

     identity weekly {
       base frequency-type;
       description
         "Indicates a repeating rule based on an interval of
          a week or more.";
     }

     identity monthly {
       base frequency-type;
       description
         "Indicates a repeating rule based on an interval of
          a month or more.";
     }

     identity yearly {
       base frequency-type;
       description
         "Indicates a repeating rule based on an interval of
          a year or more.";
     }

     identity schedule-state {
       description
         "Base identity for schedule state.";
     }

     identity enabled {
       base schedule-state;
       description
         "Indicates a schedule with an enabled state.";
     }

     identity finished {
       base schedule-state;
       description
         "Indicates a schedule with a finished state.
          The finished state indicates that the schedule has ended.";
     }

     identity disabled {
       base schedule-state;
       description
         "Indicates a schedule with a disabled state.";
     }

     identity out-of-date {
       base schedule-state;
       description
         "Indicates a schedule that is received out-of-date.";
     }

     identity conflicted {
       base schedule-state;
       description
         "Indicates a schedule with a conflicted state with other
          schedules.";
     }

     identity discard-action-type {
       description
         "Base identity for the action for the responder to take
          when a requested schedule cannot be accepted for any
          reason and is discarded.";
     }

     identity warning {
       base discard-action-type;
       description
         "Indicates that a warning message is generated
          when a schedule is discarded.";
     }

     identity error {
       base discard-action-type;
       description
         "Indicates that an error message is generated
          when a schedule is discarded.";
     }

     identity silently-discard {
       base discard-action-type;
       description
         "Indicates that a schedule that is not valid is silently
          discarded.";
     }

     grouping generic-schedule-params {
       description
         "Includes a set of generic parameters that are followed by
          the entity that supports schedules.

          Such parameters are used as guards to prevent, e.g., stale
          configuration.";
       leaf description {
         type string;
         description
           "Provides a description of the schedule.";
       }
       leaf time-zone-identifier {
         type sys:timezone-name;
         description
           "Indicates the identifier for the time zone.  This parameter
            MUST be specified if any of the date and time values are
            in the format of local time.  It MUST NOT be applied to
            date and time values that are specified in the format of
            UTC or time zone offset to UTC.";
       }
       leaf validity {
         type yang:date-and-time;
         description
           "Specifies the date and time after which a schedule will not
            be considered as valid.  This parameter takes precedence
            over similar attributes that are provided at the schedule
            instance itself.";
       }
       leaf max-allowed-start {
         type yang:date-and-time;
         description
           "Specifies the maximum scheduled start date and time.
            A requested schedule whose first instance occurs after
            this value cannot be accepted by the entity.  Specifically,
            a requested schedule will be rejected if the first
            occurrence of that schedule exceeds 'max-allowed-start'.";
       }
       leaf min-allowed-start {
         type yang:date-and-time;
         description
           "Specifies the minimum scheduled start date and time.
            A requested schedule whose first instance occurs before
            this value cannot be accepted by the entity.  Specifically,
            a requested schedule will be rejected if the first
            occurrence of that schedule is scheduled before
            'min-allowed-start'.";
       }
       leaf max-allowed-end {
         type yang:date-and-time;
         description
           "A requested schedule will be rejected if the end time of
            the last occurrence exceeds 'max-allowed-end'.";
       }
       leaf discard-action {
         type identityref {
           base discard-action-type;
         }
         description
           "Specifies the behavior when a schedule is discarded for
            any reason, e.g., failing to satisfy the guards in this
            grouping or being received out-of-date.";
       }
     }

     grouping period-of-time {
       description
         "This grouping is defined for the period of time property.";
       reference
         "RFC 5545: Internet Calendaring and Scheduling Core Object
                    Specification (iCalendar), Section 3.3.9";
       leaf period-description {
         type string;
         description
           "Provides a description of the period.";
       }
       leaf period-start {
         type yang:date-and-time;
         description
           "Period start time.";
       }
       leaf time-zone-identifier {
         type sys:timezone-name;
         description
           "Indicates the identifier for the time zone.  This parameter
            MUST be specified if either the 'period-start' or
            'period-end' value is reported in local time format.
            It MUST NOT be applied to date and time values that are
            specified in the format of UTC or time zone offset
            to UTC.";
       }
       choice period-type {
         description
           "Indicates the type of the time period.  Two types are
            supported.  If no choice is indicated, the period is
            considered to last forever.";
         case explicit {
           description
             "A period of time is identified by its start and its end.
              'period-start' indicates the period start.";
           leaf period-end {
             type yang:date-and-time;
             description
               "A period of time is defined by a start and end time.
                The start MUST be no later than the end.  The period
                is considered as a one-shot schedule if the end time
                is the same as the start time.";
           }
         }
         case duration {
           description
             "A period of time is defined by a start and a non-negative
              duration of time.";
           leaf duration {
             type duration {
               pattern 'P((([0-9]+)D)?(T(0[0-9]|1[0-9]|2[0-3])'
                     + ':[0-5][0-9]:[0-5][0-9]))|P([0-9]+)W';
             }
             description
               "A non-negative duration of time.  This value is
                equivalent to the format of 'duration' type except that
                the value cannot be negative.  The period is considered
                to be a one-shot schedule if the value is 0.";
           }
         }
       }
     }

     grouping recurrence-basic {
       description
         "A simple definition of recurrence.";
       leaf recurrence-description {
         type string;
         description
           "Provides a description of the recurrence.";
       }
       leaf frequency {
         type identityref {
           base frequency-type;
         }
         description
           "Specifies the frequency type of the recurrence rule.";
       }
       leaf interval {
         type uint32 {
           range "1..max";
         }
         must '../frequency' {
           error-message "Frequency must be provided.";
         }
         description
           "A positive integer representing the interval at which the
            recurrence rule repeats.  For example, within a 'daily'
            recurrence rule, a value of '8' means every eight days.";
       }
     }

     grouping recurrence-utc {
       description
         "A simple definition of recurrence with time specified in
          UTC format.";
       container recurrence-first {
         description
           "Specifies the first instance of the recurrence.  If
            unspecified, the recurrence is considered to start from
            the date and time when the recurrence pattern is first
            satisfied.";
         leaf start-time-utc {
           type yang:date-and-time;
           description
             "Defines the date and time of the first instance
              in the recurrence set.  A UTC format MUST be used.";
         }
         leaf duration {
           type uint32;
           units "seconds";
           description
             "When specified, it indicates how long the first occurrence
              lasts.  Unless specified otherwise, it also applies to all
              the other instances in the recurrence set.";
         }
       }
       choice recurrence-end {
         description
           "Modes to control the end of a recurrence rule.  If no
            choice is indicated, the recurrence rule is considered
            to repeat forever.";
         case until {
           description
             "This case defines a way that limits the end of
              a recurrence rule in an inclusive manner.";
           leaf utc-until {
             type yang:date-and-time;
             description
               "This parameter specifies a date and time value to
                inclusively terminate the recurrence in UTC format.
                That is, if the value specified by this parameter is
                synchronized with the specified recurrence rule, it
                becomes the last instance of the recurrence rule.";
           }
         }
         case count {
           description
             "This case defines the number of occurrences at which
              to terminate the recurrence rule.";
           leaf count {
             type uint32 {
               range "1..max";
             }
             description
               "The positive number of occurrences at which to
                terminate the recurrence rule.";
           }
         }
       }
       uses recurrence-basic;
     }

     grouping recurrence-with-time-zone {
       description
         "A simple definition of recurrence to specify a recurrence
          rule with a time zone.";
       container recurrence-first {
         description
           "Specifies the first instance of the recurrence.  If
            unspecified, the recurrence is considered to start from
            the date and time when the recurrence pattern is first
            satisfied.";
         leaf start-time {
           type yang:date-and-time;
           description
             "Defines the date and time of the first instance
              in the recurrence set.";
         }
         leaf duration {
           type duration;
           description
             "When specified, it indicates how long the first
              occurrence lasts.  Unless specified otherwise, it also
              applies to all the other instances in the recurrence
              set.";
         }
       }
       leaf time-zone-identifier {
         type sys:timezone-name;
         description
           "Indicates the identifier for the time zone in a time
            zone database.  This parameter MUST be specified if either
            the 'start-time' or 'until' value is reported in local
            time format.  It MUST NOT be applied to date and time
            values that are specified in the format of UTC or time
            zone offset to UTC.";
       }
       choice recurrence-end {
         description
           "Modes to terminate the recurrence rule.  If no choice is
            indicated, the recurrence rule is considered to repeat
            forever.";
         case until {
           description
             "The end of the recurrence rule is indicated by a specific
              date-and-time value in an inclusive manner.";
           leaf until {
             type yang:date-and-time;
             description
               "Specifies a date and time value to inclusively terminate
                the recurrence.  That is, if the value specified by
                this parameter is synchronized with the specified
                recurrence, it becomes the last instance of the
                recurrence.";
           }
         }
         case count {
           description
             "The end of the recurrence is indicated by the number
              of occurrences.";
           leaf count {
             type uint32 {
               range "1..max";
             }
             description
               "The positive number of occurrences at which to
                terminate the recurrence.";
           }
         }
       }
       uses recurrence-basic;
     }

     grouping recurrence-utc-with-periods {
       description
         "This grouping defines an aggregate set of repeating
          occurrences with UTC time format.  The recurrence instances
          are specified by the occurrences defined by both the
          recurrence rule and 'period-timeticks' list.  Duplicate
          instances are ignored.";
       uses recurrence-utc;
       list period-timeticks {
         key "period-start";
         description
           "A list of periods with timeticks formats.";
         leaf period-start {
           type yang:timeticks;
           must "(not(derived-from-or-self(../../frequency,"
              + "'schedule:secondly')) or (current() < 100)) and "
              + "(not(derived-from-or-self(../../frequency,"
              + "'schedule:minutely')) or (current() < 6000)) and "
              + "(not(derived-from-or-self(../../frequency,"
              + "'schedule:hourly')) or (current() < 360000)) and "
              + "(not(derived-from-or-self(../../frequency,"
              + "'schedule:daily')) or (current() < 8640000)) and "
              + "(not(derived-from-or-self(../../frequency,"
              + "'schedule:weekly')) or (current() < 60480000)) and "
              + "(not(derived-from-or-self(../../frequency,"
              + "'schedule:monthly')) or (current() < 267840000)) and "
              + "(not(derived-from-or-self(../../frequency,"
              + "'schedule:yearly')) or (current() < 3162240000))" {
             error-message
               "The 'period-start' must not exceed the frequency
                interval.";
           }
           description
             "Start time of the schedule within one recurrence.

              Given that the value is in timeticks format
              (i.e., 1/100 of a second), the values in the must
              statement translate to 100 = 1 s (secondly),
              6000 = 60 s = 1 min (minutely), and so on for all
              instances in the must statement invariant.";
         }
         leaf period-end {
           type yang:timeticks;
           description
             "End time of the schedule within one recurrence.
              The period start MUST be no later than the period
              end.";
         }
       }
     }

     grouping recurrence-time-zone-with-periods {
       description
         "This grouping defines an aggregate set of repeating
          occurrences with local time format and time zone specified.
          The recurrence instances are specified by the occurrences
          defined by both the recurrence rule and 'period' list.
          Duplicate instances are ignored.";
       uses recurrence-with-time-zone;
       list period {
         key "period-start";
         description
           "A list of periods with date-and-time formats.";
         uses period-of-time;
       }
     }

     grouping icalendar-recurrence {
       description
         "This grouping specifies properties of a recurrence rule.";
       reference
         "RFC 5545: Internet Calendaring and Scheduling Core Object
                    Specification (iCalendar), Section 3.8.5";
       uses recurrence-time-zone-with-periods;
       leaf-list bysecond {
         type uint32 {
           range "0..60";
         }
         description
           "Specifies a list of seconds within a minute.";
       }
       leaf-list byminute {
         type uint32 {
           range "0..59";
         }
         description
           "Specifies a list of minutes within an hour.";
       }
       leaf-list byhour {
         type uint32 {
           range "0..23";
         }
         description
           "Specifies a list of hours of the day.";
       }
       list byday {
         key "weekday";
         description
           "Specifies a list of days of the week.";
         leaf-list direction {
           when "derived-from-or-self(../../frequency, "
              + "'schedule:monthly') or "
              + "(derived-from-or-self(../../frequency,"
              + "'schedule:yearly') and not(../../byyearweek))";

           type int32 {
             range "-53..-1|1..53";
           }
           description
             "When specified, it indicates the nth occurrence of a
              specific day within the monthly or yearly recurrence
              rule.  For example, within a monthly rule, +1 monday
              represents the first Monday within the month, whereas
              -1 monday represents the last Monday of the month.";
         }
         leaf weekday {
           type schedule:weekday;
           description
             "Corresponds to seven days of the week.";
         }
       }
       leaf-list bymonthday {
         type int32 {
           range "-31..-1|1..31";
         }
         description
           "Specifies a list of days of the month.";
       }
       leaf-list byyearday {
         type int32 {
           range "-366..-1|1..366";
         }
         description
           "Specifies a list of days of the year.";
       }
       leaf-list byyearweek {
         when "derived-from-or-self(../frequency, 'schedule:yearly')";
         type int32 {
           range "-53..-1|1..53";
         }
         description
           "Specifies a list of weeks of the year.";
       }
       leaf-list byyearmonth {
         type uint32 {
           range "1..12";
         }
         description
           "Specifies a list of months of the year.";
       }
       leaf-list bysetpos {
         type int32 {
           range "-366..-1|1..366";
         }
         description
           "Specifies a list of values that corresponds to the nth
            occurrence within the set of recurrence instances
            specified by the rule.  It must only be used in conjunction
            with another 'byxxx' (bysecond, byminute, etc.) rule
            part.";
       }
       leaf workweek-start {
         type schedule:weekday;
         description
           "Specifies the day on which the workweek starts.";
       }
       leaf-list exception-dates {
         type yang:date-and-time;
         description
           "Defines a list of exceptions for recurrence.";
       }
     }

     grouping schedule-status {
       description
         "This grouping defines common properties of scheduling
          status.";
       leaf state {
         type identityref {
           base schedule-state;
         }
         description
           "Indicates the current state of the schedule.";
       }
       leaf version {
         type uint16;
         description
           "Indicates the version number of the schedule.";
       }
       leaf schedule-type {
         type identityref {
           base schedule-type;
         }
         description
           "Indicates the schedule type.";
       }
       leaf local-time {
         type yang:date-and-time;
         config false;
         description
           "Reports the local time as used by the entity that
            hosts the schedule.";
       }
       leaf last-update {
         type yang:date-and-time;
         config false;
         description
           "Reports the timestamp of when the schedule is last
            updated.";
       }
       leaf counter {
         when "derived-from-or-self(../schedule-type, "
            + "'schedule:recurrence')";
         type yang:counter32;
         config false;
         description
           "The number of occurrences while invoking the scheduled
            action successfully.  The count wraps around when it reaches
            the maximum value.";
       }
       leaf last-occurrence {
         when "derived-from-or-self(../schedule-type, "
            + "'schedule:recurrence')";
         type yang:date-and-time;
         config false;
         description
           "Indicates the timestamp of last occurrence.";
       }
       leaf upcoming-occurrence {
         when "derived-from-or-self(../schedule-type, "
            + "'schedule:recurrence')"
            + "and derived-from-or-self(../state, 'schedule:enabled')";
         type yang:date-and-time;
         config false;
         description
           "Indicates the timestamp of next occurrence.";
       }
       leaf last-failed-occurrence {
         when "derived-from-or-self(../schedule-type, "
            + "'schedule:recurrence')";
         type yang:date-and-time;
         config false;
         description
           "Indicates the timestamp of last failed action triggered by
            the schedule.";
       }
       leaf failure-counter {
         when "derived-from-or-self(../schedule-type, "
            + "'schedule:recurrence')";
         type yang:counter32;
         config false;
         description
           "Counts the number of failures while invoking the scheduled
            action.";
       }
     }

     grouping schedule-status-with-time-zone {
       description
         "This grouping defines common properties of scheduling
          status, including timezone.";
       leaf time-zone-identifier {
         type sys:timezone-name;
         config false;
         description
           "Indicates the identifier for the time zone in a time
            zone database.";
       }
       uses schedule-status;
     }

     grouping schedule-status-with-name {
       description
         "This grouping defines common properties of scheduling
          status, including a schedule name.";
       leaf schedule-name {
         type string;
         description
           "The schedule identifier that uniquely identifies a
            schedule within a device, controller, network, etc.
            The unicity scope depends on the implementation.";
       }
       uses schedule-status;
     }
   }
   <CODE ENDS>

7.  Security Considerations

   This section is modeled after the template described in Section 3.7
   of [YANG-GUIDE].

   The "ietf-schedule" YANG module defines a data model that is designed
   to be accessed via YANG-based management protocols, such as NETCONF
   [RFC6241] and RESTCONF [RFC8040].  These YANG-based management
   protocols (1) have to use a secure transport layer (e.g., SSH
   [RFC4252], TLS [RFC8446], and QUIC [RFC9000]) and (2) have to use
   mutual authentication.

   The Network Configuration Access Control Model (NACM) [RFC8341]
   provides the means to restrict access for particular NETCONF or
   RESTCONF users to a preconfigured subset of all available NETCONF or
   RESTCONF protocol operations and content.

   The "ietf-schedule" module defines a set of identities, types, and
   groupings.  These nodes are intended to be reused by other YANG
   modules.  The module by itself does not expose any data nodes that
   are writable, data nodes that contain read-only state, or RPCs.  As
   such, there are no additional security issues related to the "ietf-
   schedule" module that need to be considered.

   Modules that use the groupings that are defined in this document
   should identify the corresponding security considerations.  For
   example, reusing the following groupings will expose privacy-related
   information:

   *  Scheduling depends on reliable and accurate time synchronization.
      Inaccurate date and time setting can lead to scheduling events
      being triggered at incorrect intervals, potentially causing system
      failures or security vulnerabilities.

   *  Recurring events may conceal abnormal behavior or security
      threats, which may be drowned out by normal events, especially
      when they are triggered frequently.

   *  The absence of detailed logs and audit records of each occurrence
      trigger time and action results and therefore may make security
      incidents difficult to trace.

   *  Care must be taken when defining recurrences occurring very often
      and frequent that can be an additional source of attacks by
      keeping the system permanently busy with the management of
      scheduling.

8.  IANA Considerations

8.1.  The IETF XML Registry

   This document has registered the following URI in the "IETF XML
   Registry" [RFC3688].

   URI:  urn:ietf:params:xml:ns:yang:ietf-schedule
   Registrant Contact:  The IESG.
   XML:  N/A; the requested URI is an XML namespace.

8.2.  The YANG Module Names Registry

   This document has registered the following YANG module in the "YANG
   Module Names" registry [RFC6020].

   Name:  ietf-schedule
   Maintained by IANA:  N
   Namespace:  urn:ietf:params:xml:ns:yang:ietf-schedule
   Prefix:  schedule
   Reference:  RFC 9922

9.  References

9.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC3231]  Levi, D. and J. Schoenwaelder, "Definitions of Managed
              Objects for Scheduling Management Operations", RFC 3231,
              DOI 10.17487/RFC3231, January 2002,
              <https://www.rfc-editor.org/info/rfc3231>.

   [RFC3688]  Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
              DOI 10.17487/RFC3688, January 2004,
              <https://www.rfc-editor.org/info/rfc3688>.

   [RFC5545]  Desruisseaux, B., Ed., "Internet Calendaring and
              Scheduling Core Object Specification (iCalendar)",
              RFC 5545, DOI 10.17487/RFC5545, September 2009,
              <https://www.rfc-editor.org/info/rfc5545>.

   [RFC6020]  Bjorklund, M., Ed., "YANG - A Data Modeling Language for
              the Network Configuration Protocol (NETCONF)", RFC 6020,
              DOI 10.17487/RFC6020, October 2010,
              <https://www.rfc-editor.org/info/rfc6020>.

   [RFC7317]  Bierman, A. and M. Bjorklund, "A YANG Data Model for
              System Management", RFC 7317, DOI 10.17487/RFC7317, August
              2014, <https://www.rfc-editor.org/info/rfc7317>.

   [RFC7950]  Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
              RFC 7950, DOI 10.17487/RFC7950, August 2016,
              <https://www.rfc-editor.org/info/rfc7950>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC8341]  Bierman, A. and M. Bjorklund, "Network Configuration
              Access Control Model", STD 91, RFC 8341,
              DOI 10.17487/RFC8341, March 2018,
              <https://www.rfc-editor.org/info/rfc8341>.

   [RFC9911]  Schönwälder, J., Ed., "Common YANG Data Types", RFC 9911,
              DOI 10.17487/RFC9911, December 2025,
              <https://www.rfc-editor.org/info/rfc9911>.

9.2.  Informative References

   [NETMOD-ECA-POLICY]
              Wu, Q., Bryskin, I., Birkholz, H., Liu, X., and B. Claise,
              "A YANG Data model for ECA Policy Management", Work in
              Progress, Internet-Draft, draft-ietf-netmod-eca-policy-01,
              19 February 2021, <https://datatracker.ietf.org/doc/html/
              draft-ietf-netmod-eca-policy-01>.

   [NTPv5]    Lichvar, M. and T. Mizrahi, "Network Time Protocol Version
              5", Work in Progress, Internet-Draft, draft-ietf-ntp-
              ntpv5-08, 1 March 2026,
              <https://datatracker.ietf.org/doc/html/draft-ietf-ntp-
              ntpv5-08>.

   [RFC3339]  Klyne, G. and C. Newman, "Date and Time on the Internet:
              Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002,
              <https://www.rfc-editor.org/info/rfc3339>.

   [RFC4252]  Ylonen, T. and C. Lonvick, Ed., "The Secure Shell (SSH)
              Authentication Protocol", RFC 4252, DOI 10.17487/RFC4252,
              January 2006, <https://www.rfc-editor.org/info/rfc4252>.

   [RFC6241]  Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
              and A. Bierman, Ed., "Network Configuration Protocol
              (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
              <https://www.rfc-editor.org/info/rfc6241>.

   [RFC7951]  Lhotka, L., "JSON Encoding of Data Modeled with YANG",
              RFC 7951, DOI 10.17487/RFC7951, August 2016,
              <https://www.rfc-editor.org/info/rfc7951>.

   [RFC8040]  Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
              Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
              <https://www.rfc-editor.org/info/rfc8040>.

   [RFC8340]  Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams",
              BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018,
              <https://www.rfc-editor.org/info/rfc8340>.

   [RFC8345]  Clemm, A., Medved, J., Varga, R., Bahadur, N.,
              Ananthakrishnan, H., and X. Liu, "A YANG Data Model for
              Network Topologies", RFC 8345, DOI 10.17487/RFC8345, March
              2018, <https://www.rfc-editor.org/info/rfc8345>.

   [RFC8413]  Zhuang, Y., Wu, Q., Chen, H., and A. Farrel, "Framework
              for Scheduled Use of Resources", RFC 8413,
              DOI 10.17487/RFC8413, July 2018,
              <https://www.rfc-editor.org/info/rfc8413>.

   [RFC8446]  Rescorla, E., "The Transport Layer Security (TLS) Protocol
              Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
              <https://www.rfc-editor.org/info/rfc8446>.

   [RFC9000]  Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based
              Multiplexed and Secure Transport", RFC 9000,
              DOI 10.17487/RFC9000, May 2021,
              <https://www.rfc-editor.org/info/rfc9000>.

   [RFC9657]  Birrane, III, E., Kuhn, N., Qu, Y., Taylor, R., and L.
              Zhang, "Time-Variant Routing (TVR) Use Cases", RFC 9657,
              DOI 10.17487/RFC9657, October 2024,
              <https://www.rfc-editor.org/info/rfc9657>.

   [W3C.XML1.0]
              Bray, T., Ed., Paoli, J., Ed., Sperberg-McQueen, C. M.,
              Ed., Maler, E., Ed., and F. Yergeau, Ed., "Extensible
              Markup Language (XML) 1.0 (Fifth Edition)", W3C
              Recommendation, 26 November 2008,
              <https://www.w3.org/TR/2008/REC-xml-20081126/>.

   [YANG-CONFIG-SCHEDULE]
              Liu, X., Bryskin, I., Beeram, V. P., Saad, T., Shah, H.
              C., and O. G. de Dios, "A YANG Data Model for
              Configuration Scheduling", Work in Progress, Internet-
              Draft, draft-liu-netmod-yang-schedule-05, 1 March 2018,
              <https://datatracker.ietf.org/doc/html/draft-liu-netmod-
              yang-schedule-05>.

   [YANG-GUIDE]
              Bierman, A., Boucadair, M., and Q. Wu, "Guidelines for
              Authors and Reviewers of Documents Containing YANG Data
              Models", Work in Progress, Internet-Draft, draft-ietf-
              netmod-rfc8407bis-28, 5 June 2025,
              <https://datatracker.ietf.org/doc/html/draft-ietf-netmod-
              rfc8407bis-28>.

   [YANG-NAC] Ma, Q., Wu, Q., Boucadair, M., and D. King, "A YANG Data
              Model and RADIUS Extension for Policy-Based Network Access
              Control", Work in Progress, Internet-Draft, draft-ietf-
              opsawg-ucl-acl-12, 3 February 2026,
              <https://datatracker.ietf.org/doc/html/draft-ietf-opsawg-
              ucl-acl-12>.

   [YANG-OAM] Contreras, L. M., Lopez, V., and Q. Wu, "A YANG Data Model
              for Network Diagnosis using Scheduled Sequences of OAM
              Tests", Work in Progress, Internet-Draft, draft-ietf-
              opsawg-scheduling-oam-tests-04, 28 February 2026,
              <https://datatracker.ietf.org/doc/html/draft-ietf-opsawg-
              scheduling-oam-tests-04>.

   [YANG-SCHEDULE]
              Qu, Y., Lindem, A., Kinzie, E., Fedyk, D., and M.
              Blanchet, "YANG Data Model for Scheduled Attributes", Work
              in Progress, Internet-Draft, draft-ietf-tvr-schedule-yang-
              08, 9 February 2026,
              <https://datatracker.ietf.org/doc/html/draft-ietf-tvr-
              schedule-yang-08>.

Appendix A.  Examples of Scheduling Format Representation

   This section provides some examples to illustrate the use of the
   period and recurrence formats defined in Section 6.  The following
   modules are used for illustration purposes and make examples
   verifiable:

   module example-sch-usage-1 {
     yang-version 1.1;
     namespace "http://example.com/example-sch-usage-1";
     prefix "ex-schu-1";

     import ietf-schedule {
       prefix "schedule";
     }

     organization
       "Example, Inc.";

     contact
       "Support at example.com";

     description
       "Example of a module using 'generic-schedule-params' and
        'schedule-status' groupings.";

     revision "2026-02-20" {
       description "Initial version.";
       reference
         "RFC 9922: A YANG Data Model for Scheduling";
     }

     container generic-schedule-params {
       description
         "A collection of generic scheduling parameters.";
       uses schedule:generic-schedule-params;
     }
     container schedule-status {
       description
         "A collection of scheduling status.";
       uses schedule:schedule-status;
     }
   }

   module example-sch-usage-2 {
     yang-version 1.1;
     namespace "http://example.com/example-sch-usage-2";
     prefix "ex-schu2";

     import ietf-schedule {
       prefix "schedule";
     }

     organization
       "Example, Inc.";

     contact
       "Support at example.com";

     description
       "Example of a module using the 'period-of-time' grouping.";

     revision "2026-02-20" {
       description "Initial version.";
       reference
         "RFC 9922: A YANG Data Model for Scheduling";
     }

     container period-of-time {
       description
         "A container for a time period.";
       uses schedule:period-of-time;
     }
   }

   module example-sch-usage-3 {
     yang-version 1.1;
     namespace "http://example.com/example-sch-usage-3";
     prefix "ex-schu-3";

     import ietf-schedule {
       prefix "schedule";
     }

     organization
       "Example, Inc.";

     contact
       "Support at example.com";

     description
       "Example of a module using the 'recurrence-basic' grouping.";

     revision "2026-02-20" {
       description "Initial version.";
       reference
         "RFC 9922: A YANG Data Model for Scheduling";
     }

     container recurrence-basic {
       description
         "A container for a simple recurrence rule.";
       uses schedule:recurrence-basic {
         refine interval {
           default 1;
         }
       }
     }
   }

   module example-sch-usage-4 {
     yang-version 1.1;
     namespace "http://example.com/example-sch-usage-4";
     prefix "ex-schu-4";

     import ietf-schedule {
       prefix "schedule";
     }

     organization
       "Example, Inc.";

     contact
       "Support at example.com";

     description
       "Example of a module using the 'recurrence-utc' grouping.";

     revision "2026-02-20" {
       description "Initial version.";
       reference
         "RFC 9922: A YANG Data Model for Scheduling";
     }

     container recurrence-utc {
       description
         "A container for a simple recurrence rule in UTC format.";
       uses schedule:recurrence-utc;
     }
   }

   module example-sch-usage-5 {
     yang-version 1.1;
     namespace "http://example.com/example-sch-usage-5";
     prefix "ex-schu-5";

     import ietf-schedule {
       prefix "schedule";
     }

     organization
       "Example, Inc.";

     contact
       "Support at example.com";

     description
       "Example of a module using the 'recurrence-with-time-zone'
        grouping.";

     revision "2026-02-20" {
       description "Initial version.";
       reference
         "RFC 9922: A YANG Data Model for Scheduling";
     }

     container recurrence-with-time-zone {
       description
         "A container for a simple recurrence rule with a time zone.";
       uses schedule:recurrence-with-time-zone;
     }
   }

   module example-sch-usage-6 {
     yang-version 1.1;
     namespace "http://example.com/example-sch-usage-6";
     prefix "ex-schu-6";

     import ietf-schedule {
       prefix "schedule";
     }

     organization
       "Example, Inc.";

     contact
       "Support at example.com";

     description
       "Example of a module using the 'recurrence-utc-with-periods'
        grouping.";

     revision "2026-02-20" {
       description "Initial version.";
       reference
         "RFC 9922: A YANG Data Model for Scheduling";
     }

     container recurrence-utc-with-periods {
       description
         "A container for an aggregate set of repeating occurrences in
          UTC format.";
       uses schedule:recurrence-utc-with-periods;
     }
   }

   module example-sch-usage-7 {
     yang-version 1.1;
     namespace "http://example.com/example-sch-usage-7";
     prefix "ex-schu-8";

     import ietf-schedule {
       prefix "schedule";
     }

     organization
       "Example, Inc.";

     contact
       "Support at example.com";

     description
       "Example of a module using the
        'recurrence-time-zone-with-periods' grouping.";

     revision "2026-02-20" {
       description "Initial version.";
       reference
         "RFC 9922: A YANG Data Model for Scheduling";
     }

     container recurrence-time-zone-with-periods {
       description
         "A container for an aggregate set of repeating occurrences
          with a time zone.";
       uses schedule:recurrence-time-zone-with-periods;
     }
   }

   module example-sch-usage-8 {
     yang-version 1.1;
     namespace "http://example.com/example-sch-usage-8";
     prefix "ex-schu-8";

     import ietf-schedule {
       prefix "schedule";
     }

     organization
       "Example, Inc.";

     contact
       "Support at example.com";

     description
       "Example of a module using 'icalendar-recurrence' grouping.";

     revision "2026-02-20" {
       description "Initial version.";
       reference
         "RFC 9922: A YANG Data Model for Scheduling";
     }

     container icalendar-recurrence {
       description
         "A container for a scheduled iCalendar recurrence.";
       uses schedule:icalendar-recurrence {
         refine workweek-start {
           default monday;
         }
       }
     }
   }

   For each example, only the message body is provided with JSON, which
   is used for encoding per the guidance in [RFC7951].

A.1.  The "generic-schedule-params" Grouping

   Figure 10 illustrates the example of a requested schedule that needs
   to start no earlier than 08:00 AM, January 1, 2025 and end no later
   than 8:00 PM, January 31, 2025 (Beijing time).  Schedule requests
   that fail to meet the requirements are ignored by the system, as
   indicated by "discard-action".

   {
     "example-sch-usage-1:generic-schedule-params": {
       "time-zone-identifier": "China/Beijing",
       "min-allowed-start": "2025-01-01T08:00:00",
       "max-allowed-end": "2025-01-31T20:00:00",
       "discard-action": "ietf-schedule:silently-discard"
     }
   }

     Figure 10: Generic Parameters with 'max-allowed-end' for Schedule
                                 Validation

   To illustrate the difference between "max-allowed-end" and "validity"
   parameters, Figure 11 shows the example of a requested schedule that
   needs to start no earlier than 08:00 AM, January 1, 2025 (Beijing
   time).  Schedule requests that fail to meet the requirements are
   ignored by the system, as indicated by "discard-action".  The
   requested schedule may end after 8:00 PM, January 31, 2025, but any
   occurrences that are generated after that time would not be
   considered as valid.

   {
     "example-sch-usage-1:generic-schedule-params": {
       "time-zone-identifier": "China/Beijing",
       "validity": "2025-01-31T20:00:00",
       "min-allowed-start": "2025-01-01T08:00:00",
       "discard-action": "ietf-schedule:silently-discard"
     }
   }

   Figure 11: Generic Parameters with 'validity' for Schedule Validation

A.2.  The "period-of-time" Grouping

   Figure 12 shows an example of a period that starts at 08:00:00 UTC on
   January 1, 2025 and ends at 18:00:00 UTC on December 31, 2027.

   {
     "example-sch-usage-2:period-of-time": {
       "period-start": "2025-01-01T08:00:00Z",
       "period-end": "2027-12-31T18:00:00Z"
     }
   }

                    Figure 12: Simple Start/End Schedule

   An example of a period that starts at 08:00:00 UTC on January 1, 2025
   and lasts 15 days and 5 hours and 20 minutes is encoded as shown in
   Figure 13.

   {
     "example-sch-usage-2:period-of-time": {
       "period-start": "2025-01-01T08:00:00Z",
       "duration": "P15DT05:20:00"
     }
   }

                  Figure 13: Simple Schedule with Duration

   An example of a period that starts at 2:00 AM in Los Angeles on
   November 19, 2025 and lasts 20 weeks is depicted in Figure 14.

   {
     "example-sch-usage-2:period-of-time": {
       "period-start": "2025-11-19T02:00:00",
       "time-zone-identifier": "America/Los_Angeles",
       "duration": "P20W"
     }
   }

            Figure 14: Simple Schedule with Time Zone Indication

A.3.  The "recurrence-basic" Grouping

   Figure 15 indicates a recurrence of every 2 days, which starts
   immediately and repeats forever:

   {
     "example-sch-usage-3:recurrence-basic": {
       "recurrence-description": "forever recurrence rule",
       "frequency": "ietf-schedule:daily",
       "interval": 2
     }
   }

                 Figure 15: Simple Schedule with Recurrence

A.4.  The "recurrence-utc" Grouping

   Figure 16 indicates a recurrence from 8:00 AM to 9:00 AM every day,
   from December 1 to December 31, 2025 in UTC:

   {
     "example-sch-usage-4:recurrence-utc": {
       "recurrence-first": {
         "start-time-utc": "2025-12-01T08:00:00Z",
         "duration": 3600
       },
       "frequency": "ietf-schedule:daily",
       "interval": 1,
       "utc-until": "2025-12-31T23:59:59Z"
     }
   }

             Figure 16: Simple Schedule with Recurrence in UTC

A.5.  The "recurrence-with-time-zone" Grouping

   Figure 17 indicates a recurrence of every 2 hours for 10 occurrences
   that lasts 10 minutes and starts at 3 PM on December 1, 2025 in New
   York:

   {
     "example-sch-usage-5:recurrence-with-time-zone": {
       "recurrence-first": {
         "start-time": "2025-12-01T15:00:00",
         "duration": "PT00:10:00"
       },
       "time-zone-identifier": "America/New_York",
       "frequency": "ietf-schedule:hourly",
       "interval": 2,
       "count": 10
     }
   }

    Figure 17: Simple Schedule with Recurrence with Time Zone Indication

A.6.  The "recurrence-utc-with-periods" Grouping

   Figure 18 indicates a recurrence that occurs every two days starting
   at 9:00 AM and 3:00 PM for a duration of 30 minutes and 40 minutes,
   respectively, from 2025-06-01 to 2025-06-30 in UTC:

   {
     "example-sch-usage-6:recurrence-utc-with-periods": {
       "recurrence-first": {
         "start-time-utc": "2025-06-01T09:00:00Z"
       },
       "frequency": "ietf-schedule:daily",
       "interval": 2,
       "utc-until": "2025-06-30T23:59:59Z",
       "period-timeticks": [
         {
           "period-start": 3240000,
           "period-end": 3420000
         },
         {
           "period-start": 5400000,
           "period-end": 5640000
         }
       ]
     }
   }

              Figure 18: Example of Recurrence With Date Times

A.7.  The "recurrence-time-zone-with-periods" Grouping

   Figure 19 indicates a recurrence that occurs every 30 minutes and
   lasts for 15 minutes from 9:00 AM to 5:00 PM and two extra
   occurrences at 6:00 PM and 6:30 PM with each lasting for 20 minutes
   on 2025-12-01 (New York):

   {
     "example-sch-usage-7:recurrence-time-zone-with-periods": {
       "recurrence-first": {
         "start-time": "2025-12-01T09:00:00",
         "duration": "PT00:15:00"
       },
       "time-zone-identifier": "America/New_York",
       "frequency": "ietf-schedule:minutely",
       "interval": 30,
       "until": "2025-12-01T17:00:00Z",
       "period": [
         {
           "period-start": "2025-12-01T18:00:00",
           "duration": "PT00:20:00"
         },
         {
           "period-start": "2025-12-01T18:30:00",
           "duration": "PT00:20:00"
         }
       ]
     }
   }

             Figure 19: Example of Advanced Recurrence Schedule

A.8.  The "icalendar-recurrence" Grouping

   Figure 20 indicates 10 occurrences at 8:00 AM (EST) every last
   Saturday of the month starting in January 2024:

   {
     "example-sch-usage-8:icalendar-recurrence": {
       "recurrence-first": {
         "start-time": "2024-01-27T08:00:00"
       },
       "time-zone-identifier": "America/New_York",
       "frequency": "ietf-schedule:monthly",
       "count": 10,
       "byday": [
         {
           "direction": [
             -1
           ],
           "weekday": "saturday"
         }
       ]
     }
   }

                   Figure 20: Simple iCalendar Recurrence

   Figure 21 is an example of a recurrence that occurs on the last
   workday of the month until December 25, 2025, starting January 1,
   2025:

   {
     "example-sch-usage-8:icalendar-recurrence": {
       "recurrence-first": {
         "start-time": "2025-01-01T00:00:00"
       },
       "frequency": "ietf-schedule:monthly",
       "until": "2025-12-25T23:59:59",
       "byday": [
         {
           "weekday": "monday"
         },
         {
           "weekday": "tuesday"
         },
         {
           "weekday": "wednesday"
         },
         {
           "weekday": "thursday"
         },
         {
           "weekday": "friday"
         }
       ],
       "bysetpos": [
         -1
       ]
     }
   }

            Figure 21: Example of Advanced iCalendar Recurrence

   Figure 22 indicates a recurrence that occurs every 20 minutes from
   9:00 AM to 4:40 PM (UTC), with the exclusion of the occurrence
   starting at 10:20 AM on 2025-12-01:

   {
     "example-sch-usage-8:icalendar-recurrence": {
       "recurrence-first": {
         "start-time": "2025-12-01T09:00:00Z"
       },
       "until": "2025-12-01T16:40:00Z",
       "frequency": "ietf-schedule:minutely",
       "byminute": [
         0,
         20,
         40
       ],
       "byhour": [
         9,
         10,
         11,
         12,
         13,
         14,
         15,
         16
       ],
       "exception-dates": [
         "2025-12-01T10:20:00Z"
       ]
     }
   }

    Figure 22: Example of Advanced iCalendar Recurrence with Exceptions

A.9.  The "schedule-status" Grouping

   Figure 23 indicates the scheduled recurrence status of Figure 22 at
   the time of 12:15 PM on 2025-12-01 (UTC):

   {
     "example-sch-usage-1:schedule-status": {
       "state": "ietf-schedule:enabled",
       "version": 1,
       "schedule-type": "ietf-schedule:recurrence",
       "counter": 9,
       "last-occurrence": "2025-12-01T12:00:00Z",
       "upcoming-occurrence": "2025-12-01T12:20:00Z"
     }
   }

                  Figure 23: Example of a Schedule Status

   At the time of 12:15 PM on 2025-12-01 (UTC), the recurring event
   occurred at (note that the occurrence at 10:20 AM is excluded): 9:00,
   9:20, 9:40, 10:00, 10:40, 11:00, 11:20, 11:40, and 12:00.  The last
   occurrence was at 12:00, and the upcoming one is at 12:20.

Appendix B.  Examples of Using/Extending the "ietf-schedule" Module

   This non-normative section shows two examples for how the "ietf-
   schedule" module can be used or extended for scheduled events or
   attributes based on date and time.

B.1.  Example: Schedule Tasks to Execute Based on a Recurrence Rule

   Scheduled tasks can be used to execute specific actions based on
   certain recurrence rules (e.g., every Friday at 8:00 AM).  The
   following example module, which "uses" the "icalendar-recurrence"
   grouping from the "ietf-schedule" module, shows how a scheduled task
   could be defined with different features used for options.

   module example-scheduled-backup {
     yang-version 1.1;
     namespace "http://example.com/example-scheduled-backup";
     prefix "ex-scback";

     import ietf-inet-types {
       prefix "inet";
     }

     import ietf-schedule {
       prefix "schedule";
     }

     organization
       "Example, Inc.";

     contact
       "Support at example.com";

     description
       "Example of a module defining a scheduled-based backup
        operation.";

     revision "2026-02-20" {
       description
         "Initial version.";
       reference
         "RFC 9922: A YANG Data Model for Scheduling";
       }

     container scheduled-backup-tasks {
       description
         "A container for backing up all current running configurations
          on the device.";
       list tasks {
         key "task-id";
         description
           "The list of backing up tasks on this device.";
         leaf task-id {
           type string;
           description
             "The task identifier that uniquely identifies a scheduled
              backup task.";
         }
         choice local-or-remote {
           description
             "Specifies whether the configuration to be backed up is
              local or remote.";
           case local {
             description
               "Configuration parameters for the backing up of local
                devices.";
             leaf local {
               type empty;
               description
                 "The parameter specifies the configuration to be
                  backed up is on the local device.";
             }
           }
           case remote {
             description
               "Configuration parameters for backing up of remote
                devices.";
             leaf remote {
               type inet:domain-name;
               description
                 "The parameter specifies the remote device domain
                  name.";
             }
           }
         }

         container basic-recurrence-schedules {
           if-feature schedule:basic-recurrence;
           description
             "Basic recurrence schedule specification, which only
              applies when the schedule:basic-recurrence feature
              is supported.";
           leaf schedule-id {
             type string;
             description
               "The schedule identifier for this recurrence rule.";
           }
           uses schedule:recurrence-basic {
             refine frequency {
               mandatory true;
             }
             refine interval {
               default 1;
             }
           }
         }

         container icalendar-recurrence-schedules {
           if-feature schedule:icalendar-recurrence;
           description
             "Basic recurrence schedule specification, which only
              applies when the schedule:icalendar-recurrence feature
              is supported.";
           leaf schedule-id {
             type string;
             description
               "The schedule identifier for this recurrence rule.";
           }
           uses schedule:icalendar-recurrence {
             refine workweek-start {
               default monday;
             }
           }
         }
       }

       list schedule-set {
         key "schedule-name";
         description
           "Schedule status list for the backup tasks.";
         uses schedule:schedule-status-with-name;
       }
     }
   }

B.2.  Example: Schedule Network Properties to Change Based on Date and
      Time

   Network properties may change over a specific period of time or based
   on a recurrence rule, e.g., [RFC9657].  The following example module,
   which augments the "recurrence-utc-with-periods" grouping from the
   "ietf-schedule" module, shows how a scheduled attribute could be
   defined.  Note that [RFC8345] and this document are referenced in the
   module.

   module example-scheduled-link-bandwidth {
     yang-version 1.1;
     namespace "http://example.com/example-scheduled-link-bandwidth";
     prefix "ex-scattr";

     import ietf-network {
       prefix "nw";
       reference
         "RFC 8345: A YANG Data Model for Network Topologies";
     }

     import ietf-schedule {
       prefix "schedule";
       reference
         "RFC 9922: A YANG Data Model for Scheduling";
     }

     organization
       "Example, Inc.";

     contact
       "Support at example.com";

     description
       "Example of a module defining a scheduled link bandwidth.";

     revision "2026-02-20" {
       description
         "Initial version.";
       reference
         "RFC 9922: A YANG Data Model for Scheduling";
       }

     grouping link-bandwidth-grouping {
       description
         "Grouping of the link bandwidth definition.";
       leaf scheduled-bandwidth {
         type uint64;
         units "Kbps";
         description
           "Bandwidth values, expressed in kilobits per second.";
       }
     }

     container link-attributes {
       description
         "Definition of link attributes.";
       list link {
         key "source-node destination-node";
         description
           "Definition of link attributes.";
         leaf source-node {
           type nw:node-id;
           description
             "Indicates the source node identifier.";
         }
         leaf destination-node {
           type nw:node-id;
           description
             "Indicates the source node identifier.";
         }

         leaf default-bandwidth {
           type uint64;
           units "Kbps";
           description
             "Bandwidth value used for periods that don't match
              a schedule.";
         }

         choice time-variant-type {
           description
             "Controls the schedule type.";
           case period {
             uses schedule:period-of-time;
           }
           case recurrence {
             uses schedule:recurrence-utc-with-periods {
               augment "period-timeticks" {
                 description
                   "Specifies the attributes inside each
                    'period-timeticks' entry.";
                 uses link-bandwidth-grouping;
               }
             }
           }
         }
       }
     }
   }

   Figure 24 shows a configuration example in XML [W3C.XML1.0] of a
   link's bandwidth that is scheduled between 2025-12-01 0:00 UTC to the
   end of 2025-12-31 with a daily schedule.  In each day, the bandwidth
   value is scheduled to be 500 Kbps between 1:00 AM to 6:00 AM and 800
   Kbps between 10:00 PM to 11:00 PM.  The bandwidth value that is not
   covered by the period above is 1000 Kbps.

   <?xml version="1.0" encoding="utf-8"?>
   <link-attributes
     xmlns="http://example.com/example-scheduled-link-bandwidth"
     xmlns:schedule="urn:ietf:params:xml:ns:yang:ietf-schedule">
     <link>
       <source-node>ne1</source-node>
       <destination-node>ne2</destination-node>
       <default-bandwidth>1000</default-bandwidth>
       <recurrence-first>
         <start-time-utc>2025-12-01T01:00:00Z</start-time-utc>
       </recurrence-first>
       <frequency>schedule:daily</frequency>
       <utc-until>2025-12-31T23:59:59Z</utc-until>
       <period-timeticks>
         <period-start>360000</period-start>
         <period-end>2160000</period-end>
         <scheduled-bandwidth>500</scheduled-bandwidth>
       </period-timeticks>
       <period-timeticks>
         <period-start>7920000</period-start>
         <period-end>8280000</period-end>
         <scheduled-bandwidth>800</scheduled-bandwidth>
       </period-timeticks>
     </link>
   </link-attributes>

              Figure 24: Example of Scheduled Link's Bandwidth

Appendix C.  Examples of Using the "ietf-schedule" Module for Scheduled
             Use of Resources Framework

   This section exemplifies how the architecture for supporting
   scheduled reservation of Traffic Engineering (TE) resources in
   [RFC8413] might leverage the "period-of-time" grouping defined in the
   "ietf-schedule" module to implement scheduled use of resources.

   The following example module shows how a scheduled link capacity
   reservation could be defined.

   module example-sch-capacity-res {
     yang-version 1.1;
     namespace "http://example.com/example-sch-capacity-res";
     prefix "ex-schecaparev";

     import ietf-network-topology {
       prefix "nt";
     }

     import ietf-schedule {
       prefix "schedule";
     }

     organization
       "Example, Inc.";

     contact
       "Support at example.com";

     description
       "An example to show a scheduled link capacity reservation.";

     revision "2026-02-20" {
       description
         "Initial version.";
       reference
         "RFC 9922: A YANG Data Model for Scheduling";
     }

     container link-capability-reservations {
       description
         "A container for a scheduled link capability reservations.";
       list scheduled-link-capacity {
         key "schedule-id";
         description
           "Definition of scheduled link capacity list.";
         leaf schedule-id {
           type string;
           description
             "The schedule identifier for this schedule rule.";
         }
         leaf link-id {
           type nt:link-id;
           description
             "The identifier of a link in the topology.";
         }
         leaf reserved-capability {
           type uint64;
           units "Mbps";
           description
             "The reserved capability for a particular link.";
         }
         uses schedule:period-of-time;
       }
     }
   }

   Section 4 of [RFC8413] defines the reference architecture for
   scheduled use of resources.  The service requester sends a request to
   a Path Computation Element (PCE) and includes the parameters of the
   Label Switched Path (LSP) that the requester wishes to supply.  The
   configuration example to provide the scheduled resource is shown in
   Figure 25.

   <?xml version="1.0" encoding="utf-8"?>
   <link-capability-reservations
     xmlns="http://example.com/example-sch-capacity-res"
     xmlns:schedule="urn:ietf:params:xml:ns:yang:ietf-schedule">
      <scheduled-link-capacity>
         <schedule-id>1</schedule-id>
         <link-id>1-2-1</link-id>
         <reserved-capability>500</reserved-capability>
         <period-start>2025-03-10T08:00:00Z</period-start>
         <period-end>2025-03-10T09:00:00Z</period-end>
      </scheduled-link-capacity>
      <scheduled-link-capacity>
         <schedule-id>2</schedule-id>
         <link-id>2-1-1</link-id>
         <reserved-capability>400</reserved-capability>
         <period-start>2025-04-01T00:00:00Z</period-start>
         <duration>PT09:00:00</duration>
      </scheduled-link-capacity>
      <scheduled-link-capacity>
         <schedule-id>3</schedule-id>
         <link-id>2-1-1</link-id>
         <reserved-capability>500</reserved-capability>
         <period-start>2025-04-01T09:00:00Z</period-start>
         <period-end>2025-04-01T23:59:59Z</period-end>
      </scheduled-link-capacity>
   </link-capability-reservations>

        Figure 25: Example of Scheduled Link's Bandwidth Reservation

Acknowledgments

   This work is derived from [YANG-NAC].  There is a desire from the
   OPSAWG to see this module separately defined for wide use in
   scheduling context.

   Thanks to Adrian Farrel, Wei Pan, Tianran Zhou, Joe Clarke, Steve
   Baillargeon, Dhruv Dhody, Robert Wilton, and Italo Busi for their
   valuable comments and inputs to this work.

   Many thanks to the authors of [YANG-SCHEDULE], [YANG-OAM], and
   [NETMOD-ECA-POLICY] for the constructive discussion during IETF#118.

   Other related efforts were explored in the past, e.g.,
   [YANG-CONFIG-SCHEDULE].

   Thanks to Reshad Rahman for the great YANG Doctors review, Mahesh
   Jethanandani for the AD review, Per Andersson for the OPSDIR review,
   Peter Yee for the GENART review, and Acee Lindem for the RTGDIR
   review.

   Thanks to Éric Vyncke, Erik Kline, and Mike Bishop for the IESG
   review.

Authors' Addresses

   Qiufang Ma (editor)
   Huawei
   101 Software Avenue, Yuhua District
   Jiangsu
   210012
   China
   Email: maqiufang1@huawei.com


   Qin Wu
   Huawei
   101 Software Avenue, Yuhua District
   Jiangsu
   210012
   China
   Email: bill.wu@huawei.com


   Mohamed Boucadair (editor)
   Orange
   35000 Rennes
   France
   Email: mohamed.boucadair@orange.com


   Daniel King
   Lancaster University
   United Kingdom
   Email: d.king@lancaster.ac.uk
