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  4. [ iCalendar (RFC 5545)  ](/RFC-Specifications/iCalendar-RFC-5545/)
  5. 3.8.7.4. Sequence Number 

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#  3.8.7.4. Sequence Number

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##  Property Name

SEQUENCE

##  Purpose

This property defines the revision sequence number of the calendar component
within a sequence of revisions.

##  Value Type

INTEGER

##  Property Parameters

IANA and non-standard property parameters can be specified on this property.
Conformance: The property can be specified in [ "VEVENT" ](/iCalendar-
RFC-5545/3-6-1-event-component.html) , [ "VTODO" ](/iCalendar-
RFC-5545/3-6-2-to-do-component.html) , or [ "VJOURNAL" ](/iCalendar-
RFC-5545/3-6-3-journal-component.html) calendar component.

##  Description

When a calendar component is created, its sequence number is 0. It is
monotonically incremented by the "Organizer's" CUA each time the "Organizer"
makes a significant revision to the calendar component.

The "Organizer" includes this property in an iCalendar object that it sends to
an "Attendee" to specify the current version of the calendar component.

The "Attendee" includes this property in an iCalendar object that it sends to
the "Organizer" to specify the version of the calendar component to which the
"Attendee" is referring.

A change to the sequence number is not the mechanism that an "Organizer" uses
to request a response from the "Attendees". The "RSVP" parameter on the [
"ATTENDEE" ](/iCalendar-RFC-5545/3-8-4-1-attendee.html) property is used by
the "Organizer" to indicate that a response from the "Attendees" is requested.

Recurrence instances of a recurring component MAY have different sequence
numbers.

##  Format Definition

This property is defined by the following notation:

    
    
     seq = ["SEQUENCE"](/iCalendar-RFC-5545/3-8-7-4-sequence-number.html) seqparam ":" integer CRLF
     ; Default is "0"
    
    
     seqparam   = *(";" other-param)

##  Example

The following is an example of this property for a calendar component that was
just created by the "Organizer":

    
    
     SEQUENCE:0

The following is an example of this property for a calendar component that has
been revised two different times by the "Organizer":

    
    
     SEQUENCE:2

[ Previous article: 3.8.7.3. Last Modified  Prev  ](/iCalendar-
RFC-5545/3-8-7-3-last-modified.html) [ Next article: 3.8.8. Miscellaneous
Component Properties  Next  ](/iCalendar-RFC-5545/3-8-8-miscellaneous-
component-properties.html)

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document should be referred to if there are any errors or discrepancies found
in this document. _

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