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RFC 5545

 
 
 

Internet Calendaring and Scheduling Core Object Specification (iCalendar)

Part 5 of 7, p. 94 to 118
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3.8.2.  Date and Time Component Properties

   The following properties specify date and time related information in
   calendar components.

3.8.2.1.  Date-Time Completed

   Property Name:  COMPLETED

   Purpose:  This property defines the date and time that a to-do was
      actually completed.

   Value Type:  DATE-TIME

   Property Parameters:  IANA and non-standard property parameters can
      be specified on this property.

   Conformance:  The property can be specified in a "VTODO" calendar
      component.  The value MUST be specified as a date with UTC time.

   Description:  This property defines the date and time that a to-do
      was actually completed.

   Format Definition:  This property is defined by the following
      notation:

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       completed  = "COMPLETED" compparam ":" date-time CRLF

       compparam  = *(";" other-param)

   Example:  The following is an example of this property:

    COMPLETED:19960401T150000Z

3.8.2.2.  Date-Time End

   Property Name:  DTEND

   Purpose:  This property specifies the date and time that a calendar
      component ends.

   Value Type:  The default value type is DATE-TIME.  The value type can
      be set to a DATE value type.

   Property Parameters:  IANA, non-standard, value data type, and time
      zone identifier property parameters can be specified on this
      property.

   Conformance:  This property can be specified in "VEVENT" or
      "VFREEBUSY" calendar components.

   Description:  Within the "VEVENT" calendar component, this property
      defines the date and time by which the event ends.  The value type
      of this property MUST be the same as the "DTSTART" property, and
      its value MUST be later in time than the value of the "DTSTART"
      property.  Furthermore, this property MUST be specified as a date
      with local time if and only if the "DTSTART" property is also
      specified as a date with local time.

      Within the "VFREEBUSY" calendar component, this property defines
      the end date and time for the free or busy time information.  The
      time MUST be specified in the UTC time format.  The value MUST be
      later in time than the value of the "DTSTART" property.

   Format Definition:  This property is defined by the following
      notation:

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       dtend      = "DTEND" dtendparam ":" dtendval CRLF

       dtendparam = *(
                  ;
                  ; The following are OPTIONAL,
                  ; but MUST NOT occur more than once.
                  ;
                  (";" "VALUE" "=" ("DATE-TIME" / "DATE")) /
                  (";" tzidparam) /
                  ;
                  ; The following is OPTIONAL,
                  ; and MAY occur more than once.
                  ;
                  (";" other-param)
                  ;
                  )

       dtendval   = date-time / date
       ;Value MUST match value type

   Example:  The following is an example of this property:

       DTEND:19960401T150000Z

       DTEND;VALUE=DATE:19980704

3.8.2.3.  Date-Time Due

   Property Name:  DUE

   Purpose:  This property defines the date and time that a to-do is
      expected to be completed.

   Value Type:  The default value type is DATE-TIME.  The value type can
      be set to a DATE value type.

   Property Parameters:  IANA, non-standard, value data type, and time
      zone identifier property parameters can be specified on this
      property.

   Conformance:  The property can be specified once in a "VTODO"
      calendar component.

   Description:  This property defines the date and time before which a
      to-do is expected to be completed.  For cases where this property
      is specified in a "VTODO" calendar component that also specifies a
      "DTSTART" property, the value type of this property MUST be the
      same as the "DTSTART" property, and the value of this property

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      MUST be later in time than the value of the "DTSTART" property.
      Furthermore, this property MUST be specified as a date with local
      time if and only if the "DTSTART" property is also specified as a
      date with local time.

   Format Definition:  This property is defined by the following
      notation:

       due        = "DUE" dueparam ":" dueval CRLF

       dueparam   = *(
                  ;
                  ; The following are OPTIONAL,
                  ; but MUST NOT occur more than once.
                  ;
                  (";" "VALUE" "=" ("DATE-TIME" / "DATE")) /
                  (";" tzidparam) /
                  ;
                  ; The following is OPTIONAL,
                  ; and MAY occur more than once.
                  ;
                  (";" other-param)
                  ;
                  )

       dueval     = date-time / date
       ;Value MUST match value type

   Example:  The following is an example of this property:

       DUE:19980430T000000Z

3.8.2.4.  Date-Time Start

   Property Name:  DTSTART

   Purpose:  This property specifies when the calendar component begins.

   Value Type:  The default value type is DATE-TIME.  The time value
      MUST be one of the forms defined for the DATE-TIME value type.
      The value type can be set to a DATE value type.

   Property Parameters:  IANA, non-standard, value data type, and time
      zone identifier property parameters can be specified on this
      property.

   Conformance:  This property can be specified once in the "VEVENT",
      "VTODO", or "VFREEBUSY" calendar components as well as in the

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      "STANDARD" and "DAYLIGHT" sub-components.  This property is
      REQUIRED in all types of recurring calendar components that
      specify the "RRULE" property.  This property is also REQUIRED in
      "VEVENT" calendar components contained in iCalendar objects that
      don't specify the "METHOD" property.

   Description:  Within the "VEVENT" calendar component, this property
      defines the start date and time for the event.

      Within the "VFREEBUSY" calendar component, this property defines
      the start date and time for the free or busy time information.
      The time MUST be specified in UTC time.

      Within the "STANDARD" and "DAYLIGHT" sub-components, this property
      defines the effective start date and time for a time zone
      specification.  This property is REQUIRED within each "STANDARD"
      and "DAYLIGHT" sub-components included in "VTIMEZONE" calendar
      components and MUST be specified as a date with local time without
      the "TZID" property parameter.

   Format Definition:  This property is defined by the following
      notation:

       dtstart    = "DTSTART" dtstparam ":" dtstval CRLF

       dtstparam  = *(
                  ;
                  ; The following are OPTIONAL,
                  ; but MUST NOT occur more than once.
                  ;
                  (";" "VALUE" "=" ("DATE-TIME" / "DATE")) /
                  (";" tzidparam) /
                  ;
                  ; The following is OPTIONAL,
                  ; and MAY occur more than once.
                  ;
                  (";" other-param)
                  ;
                  )

       dtstval    = date-time / date
       ;Value MUST match value type

   Example:  The following is an example of this property:

       DTSTART:19980118T073000Z

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3.8.2.5.  Duration

   Property Name:  DURATION

   Purpose:  This property specifies a positive duration of time.

   Value Type:  DURATION

   Property Parameters:  IANA and non-standard property parameters can
      be specified on this property.

   Conformance:  This property can be specified in "VEVENT", "VTODO", or
      "VALARM" calendar components.

   Description:  In a "VEVENT" calendar component the property may be
      used to specify a duration of the event, instead of an explicit
      end DATE-TIME.  In a "VTODO" calendar component the property may
      be used to specify a duration for the to-do, instead of an
      explicit due DATE-TIME.  In a "VALARM" calendar component the
      property may be used to specify the delay period prior to
      repeating an alarm.  When the "DURATION" property relates to a
      "DTSTART" property that is specified as a DATE value, then the
      "DURATION" property MUST be specified as a "dur-day" or "dur-week"
      value.

   Format Definition:  This property is defined by the following
      notation:

       duration   = "DURATION" durparam ":" dur-value CRLF
                    ;consisting of a positive duration of time.

       durparam   = *(";" other-param)

   Example:  The following is an example of this property that specifies
      an interval of time of one hour and zero minutes and zero seconds:

       DURATION:PT1H0M0S

      The following is an example of this property that specifies an
      interval of time of 15 minutes.

       DURATION:PT15M

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3.8.2.6.  Free/Busy Time

   Property Name:  FREEBUSY

   Purpose:  This property defines one or more free or busy time
      intervals.

   Value Type:  PERIOD

   Property Parameters:  IANA, non-standard, and free/busy time type
      property parameters can be specified on this property.

   Conformance:  The property can be specified in a "VFREEBUSY" calendar
      component.

   Description:  These time periods can be specified as either a start
      and end DATE-TIME or a start DATE-TIME and DURATION.  The date and
      time MUST be a UTC time format.

      "FREEBUSY" properties within the "VFREEBUSY" calendar component
      SHOULD be sorted in ascending order, based on start time and then
      end time, with the earliest periods first.

      The "FREEBUSY" property can specify more than one value, separated
      by the COMMA character.  In such cases, the "FREEBUSY" property
      values MUST all be of the same "FBTYPE" property parameter type
      (e.g., all values of a particular "FBTYPE" listed together in a
      single property).

   Format Definition:  This property is defined by the following
      notation:

       freebusy   = "FREEBUSY" fbparam ":" fbvalue CRLF

       fbparam    = *(
                  ;
                  ; The following is OPTIONAL,
                  ; but MUST NOT occur more than once.
                  ;
                  (";" fbtypeparam) /
                  ;
                  ; The following is OPTIONAL,
                  ; and MAY occur more than once.
                  ;
                  (";" other-param)
                  ;
                  )

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       fbvalue    = period *("," period)
       ;Time value MUST be in the UTC time format.

   Example:  The following are some examples of this property:

       FREEBUSY;FBTYPE=BUSY-UNAVAILABLE:19970308T160000Z/PT8H30M

       FREEBUSY;FBTYPE=FREE:19970308T160000Z/PT3H,19970308T200000Z/PT1H

       FREEBUSY;FBTYPE=FREE:19970308T160000Z/PT3H,19970308T200000Z/PT1H
        ,19970308T230000Z/19970309T000000Z

3.8.2.7.  Time Transparency

   Property Name:  TRANSP

   Purpose:  This property defines whether or not an event is
      transparent to busy time searches.

   Value Type:  TEXT

   Property Parameters:  IANA and non-standard property parameters can
      be specified on this property.

   Conformance:  This property can be specified once in a "VEVENT"
      calendar component.

   Description:  Time Transparency is the characteristic of an event
      that determines whether it appears to consume time on a calendar.
      Events that consume actual time for the individual or resource
      associated with the calendar SHOULD be recorded as OPAQUE,
      allowing them to be detected by free/busy time searches.  Other
      events, which do not take up the individual's (or resource's) time
      SHOULD be recorded as TRANSPARENT, making them invisible to free/
      busy time searches.

   Format Definition:  This property is defined by the following
      notation:

       transp     = "TRANSP" transparam ":" transvalue CRLF

       transparam = *(";" other-param)

       transvalue = "OPAQUE"
                   ;Blocks or opaque on busy time searches.
                   / "TRANSPARENT"
                   ;Transparent on busy time searches.
       ;Default value is OPAQUE

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   Example:  The following is an example of this property for an event
      that is transparent or does not block on free/busy time searches:

       TRANSP:TRANSPARENT

      The following is an example of this property for an event that is
      opaque or blocks on free/busy time searches:

       TRANSP:OPAQUE

3.8.3.  Time Zone Component Properties

   The following properties specify time zone information in calendar
   components.

3.8.3.1.  Time Zone Identifier

   Property Name:  TZID

   Purpose:  This property specifies the text value that uniquely
      identifies the "VTIMEZONE" calendar component in the scope of an
      iCalendar object.

   Value Type:  TEXT

   Property Parameters:  IANA and non-standard property parameters can
      be specified on this property.

   Conformance:  This property MUST be specified in a "VTIMEZONE"
      calendar component.

   Description:  This is the label by which a time zone calendar
      component is referenced by any iCalendar properties whose value
      type is either DATE-TIME or TIME and not intended to specify a UTC
      or a "floating" time.  The presence of the SOLIDUS character as a
      prefix, indicates that this "TZID" represents an unique ID in a
      globally defined time zone registry (when such registry is
      defined).

         Note: This document does not define a naming convention for
         time zone identifiers.  Implementers may want to use the naming
         conventions defined in existing time zone specifications such
         as the public-domain TZ database [TZDB].  The specification of
         globally unique time zone identifiers is not addressed by this
         document and is left for future study.

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   Format Definition:  This property is defined by the following
      notation:

       tzid       = "TZID" tzidpropparam ":" [tzidprefix] text CRLF

       tzidpropparam      = *(";" other-param)

       ;tzidprefix        = "/"
       ; Defined previously. Just listed here for reader convenience.

   Example:  The following are examples of non-globally unique time zone
      identifiers:

       TZID:America/New_York

       TZID:America/Los_Angeles

      The following is an example of a fictitious globally unique time
      zone identifier:

       TZID:/example.org/America/New_York

3.8.3.2.  Time Zone Name

   Property Name:  TZNAME

   Purpose:  This property specifies the customary designation for a
      time zone description.

   Value Type:  TEXT

   Property Parameters:  IANA, non-standard, and language property
      parameters can be specified on this property.

   Conformance:  This property can be specified in "STANDARD" and
      "DAYLIGHT" sub-components.

   Description:  This property specifies a customary name that can be
      used when displaying dates that occur during the observance
      defined by the time zone sub-component.

   Format Definition:  This property is defined by the following
      notation:

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       tzname     = "TZNAME" tznparam ":" text CRLF

       tznparam   = *(
                  ;
                  ; The following is OPTIONAL,
                  ; but MUST NOT occur more than once.
                  ;
                  (";" languageparam) /
                  ;
                  ; The following is OPTIONAL,
                  ; and MAY occur more than once.
                  ;
                  (";" other-param)
                  ;
                  )

   Example:  The following are examples of this property:

       TZNAME:EST

       TZNAME;LANGUAGE=fr-CA:HNE

3.8.3.3.  Time Zone Offset From

   Property Name:  TZOFFSETFROM

   Purpose:  This property specifies the offset that is in use prior to
      this time zone observance.

   Value Type:  UTC-OFFSET

   Property Parameters:  IANA and non-standard property parameters can
      be specified on this property.

   Conformance:  This property MUST be specified in "STANDARD" and
      "DAYLIGHT" sub-components.

   Description:  This property specifies the offset that is in use prior
      to this time observance.  It is used to calculate the absolute
      time at which the transition to a given observance takes place.
      This property MUST only be specified in a "VTIMEZONE" calendar
      component.  A "VTIMEZONE" calendar component MUST include this
      property.  The property value is a signed numeric indicating the
      number of hours and possibly minutes from UTC.  Positive numbers
      represent time zones east of the prime meridian, or ahead of UTC.
      Negative numbers represent time zones west of the prime meridian,
      or behind UTC.

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   Format Definition:  This property is defined by the following
      notation:

       tzoffsetfrom       = "TZOFFSETFROM" frmparam ":" utc-offset
                            CRLF

       frmparam   = *(";" other-param)

   Example:  The following are examples of this property:

       TZOFFSETFROM:-0500

       TZOFFSETFROM:+1345

3.8.3.4.  Time Zone Offset To

   Property Name:  TZOFFSETTO

   Purpose:  This property specifies the offset that is in use in this
      time zone observance.

   Value Type:  UTC-OFFSET

   Property Parameters:  IANA and non-standard property parameters can
      be specified on this property.

   Conformance:  This property MUST be specified in "STANDARD" and
      "DAYLIGHT" sub-components.

   Description:  This property specifies the offset that is in use in
      this time zone observance.  It is used to calculate the absolute
      time for the new observance.  The property value is a signed
      numeric indicating the number of hours and possibly minutes from
      UTC.  Positive numbers represent time zones east of the prime
      meridian, or ahead of UTC.  Negative numbers represent time zones
      west of the prime meridian, or behind UTC.

   Format Definition:  This property is defined by the following
      notation:

       tzoffsetto = "TZOFFSETTO" toparam ":" utc-offset CRLF

       toparam    = *(";" other-param)

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   Example:  The following are examples of this property:

       TZOFFSETTO:-0400

       TZOFFSETTO:+1245

3.8.3.5.  Time Zone URL

   Property Name:  TZURL

   Purpose:  This property provides a means for a "VTIMEZONE" component
      to point to a network location that can be used to retrieve an up-
      to-date version of itself.

   Value Type:  URI

   Property Parameters:  IANA and non-standard property parameters can
      be specified on this property.

   Conformance:  This property can be specified in a "VTIMEZONE"
      calendar component.

   Description:  This property provides a means for a "VTIMEZONE"
      component to point to a network location that can be used to
      retrieve an up-to-date version of itself.  This provides a hook to
      handle changes government bodies impose upon time zone
      definitions.  Retrieval of this resource results in an iCalendar
      object containing a single "VTIMEZONE" component and a "METHOD"
      property set to PUBLISH.

   Format Definition:  This property is defined by the following
      notation:

       tzurl      = "TZURL" tzurlparam ":" uri CRLF

       tzurlparam = *(";" other-param)

   Example:  The following is an example of this property:

    TZURL:http://timezones.example.org/tz/America-Los_Angeles.ics

3.8.4.  Relationship Component Properties

   The following properties specify relationship information in calendar
   components.

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3.8.4.1.  Attendee

   Property Name:  ATTENDEE

   Purpose:  This property defines an "Attendee" within a calendar
      component.

   Value Type:  CAL-ADDRESS

   Property Parameters:  IANA, non-standard, language, calendar user
      type, group or list membership, participation role, participation
      status, RSVP expectation, delegatee, delegator, sent by, common
      name, or directory entry reference property parameters can be
      specified on this property.

   Conformance:  This property MUST be specified in an iCalendar object
      that specifies a group-scheduled calendar entity.  This property
      MUST NOT be specified in an iCalendar object when publishing the
      calendar information (e.g., NOT in an iCalendar object that
      specifies the publication of a calendar user's busy time, event,
      to-do, or journal).  This property is not specified in an
      iCalendar object that specifies only a time zone definition or
      that defines calendar components that are not group-scheduled
      components, but are components only on a single user's calendar.

   Description:  This property MUST only be specified within calendar
      components to specify participants, non-participants, and the
      chair of a group-scheduled calendar entity.  The property is
      specified within an "EMAIL" category of the "VALARM" calendar
      component to specify an email address that is to receive the email
      type of iCalendar alarm.

      The property parameter "CN" is for the common or displayable name
      associated with the calendar address; "ROLE", for the intended
      role that the attendee will have in the calendar component;
      "PARTSTAT", for the status of the attendee's participation;
      "RSVP", for indicating whether the favor of a reply is requested;
      "CUTYPE", to indicate the type of calendar user; "MEMBER", to
      indicate the groups that the attendee belongs to; "DELEGATED-TO",
      to indicate the calendar users that the original request was
      delegated to; and "DELEGATED-FROM", to indicate whom the request
      was delegated from; "SENT-BY", to indicate whom is acting on
      behalf of the "ATTENDEE"; and "DIR", to indicate the URI that
      points to the directory information corresponding to the attendee.
      These property parameters can be specified on an "ATTENDEE"
      property in either a "VEVENT", "VTODO", or "VJOURNAL" calendar
      component.  They MUST NOT be specified in an "ATTENDEE" property
      in a "VFREEBUSY" or "VALARM" calendar component.  If the

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      "LANGUAGE" property parameter is specified, the identified
      language applies to the "CN" parameter.

      A recipient delegated a request MUST inherit the "RSVP" and "ROLE"
      values from the attendee that delegated the request to them.

      Multiple attendees can be specified by including multiple
      "ATTENDEE" properties within the calendar component.

   Format Definition:  This property is defined by the following
      notation:

       attendee   = "ATTENDEE" attparam ":" cal-address CRLF

       attparam   = *(
                  ;
                  ; The following are OPTIONAL,
                  ; but MUST NOT occur more than once.
                  ;
                  (";" cutypeparam) / (";" memberparam) /
                  (";" roleparam) / (";" partstatparam) /
                  (";" rsvpparam) / (";" deltoparam) /
                  (";" delfromparam) / (";" sentbyparam) /
                  (";" cnparam) / (";" dirparam) /
                  (";" languageparam) /
                  ;
                  ; The following is OPTIONAL,
                  ; and MAY occur more than once.
                  ;
                  (";" other-param)
                  ;
                  )

   Example:  The following are examples of this property's use for a
      to-do:

       ATTENDEE;MEMBER="mailto:DEV-GROUP@example.com":
        mailto:joecool@example.com
       ATTENDEE;DELEGATED-FROM="mailto:immud@example.com":
        mailto:ildoit@example.com

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      The following is an example of this property used for specifying
      multiple attendees to an event:

       ATTENDEE;ROLE=REQ-PARTICIPANT;PARTSTAT=TENTATIVE;CN=Henry
        Cabot:mailto:hcabot@example.com
       ATTENDEE;ROLE=REQ-PARTICIPANT;DELEGATED-FROM="mailto:bob@
        example.com";PARTSTAT=ACCEPTED;CN=Jane Doe:mailto:jdoe@
        example.com

      The following is an example of this property with a URI to the
      directory information associated with the attendee:

       ATTENDEE;CN=John Smith;DIR="ldap://example.com:6666/o=ABC%
        20Industries,c=US???(cn=Jim%20Dolittle)":mailto:jimdo@
        example.com

      The following is an example of this property with "delegatee" and
      "delegator" information for an event:

       ATTENDEE;ROLE=REQ-PARTICIPANT;PARTSTAT=TENTATIVE;DELEGATED-FROM=
        "mailto:iamboss@example.com";CN=Henry Cabot:mailto:hcabot@
        example.com
       ATTENDEE;ROLE=NON-PARTICIPANT;PARTSTAT=DELEGATED;DELEGATED-TO=
        "mailto:hcabot@example.com";CN=The Big Cheese:mailto:iamboss
        @example.com
       ATTENDEE;ROLE=REQ-PARTICIPANT;PARTSTAT=ACCEPTED;CN=Jane Doe
        :mailto:jdoe@example.com

   Example:  The following is an example of this property's use when
      another calendar user is acting on behalf of the "Attendee":

       ATTENDEE;SENT-BY=mailto:jan_doe@example.com;CN=John Smith:
        mailto:jsmith@example.com

3.8.4.2.  Contact

   Property Name:  CONTACT

   Purpose:  This property is used to represent contact information or
      alternately a reference to contact information associated with the
      calendar component.

   Value Type:  TEXT

   Property Parameters:  IANA, non-standard, alternate text
      representation, and language property parameters can be specified
      on this property.

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   Conformance:  This property can be specified in a "VEVENT", "VTODO",
      "VJOURNAL", or "VFREEBUSY" calendar component.

   Description:  The property value consists of textual contact
      information.  An alternative representation for the property value
      can also be specified that refers to a URI pointing to an
      alternate form, such as a vCard [RFC2426], for the contact
      information.

   Format Definition:  This property is defined by the following
      notation:

       contact    = "CONTACT" contparam ":" text CRLF

       contparam  = *(
                  ;
                  ; The following are OPTIONAL,
                  ; but MUST NOT occur more than once.
                  ;
                  (";" altrepparam) / (";" languageparam) /
                  ;
                  ; The following is OPTIONAL,
                  ; and MAY occur more than once.
                  ;
                  (";" other-param)
                  ;
                  )

   Example:  The following is an example of this property referencing
      textual contact information:

       CONTACT:Jim Dolittle\, ABC Industries\, +1-919-555-1234

      The following is an example of this property with an alternate
      representation of an LDAP URI to a directory entry containing the
      contact information:

       CONTACT;ALTREP="ldap://example.com:6666/o=ABC%20Industries\,
        c=US???(cn=Jim%20Dolittle)":Jim Dolittle\, ABC Industries\,
        +1-919-555-1234

      The following is an example of this property with an alternate
      representation of a MIME body part containing the contact
      information, such as a vCard [RFC2426] embedded in a text/
      directory media type [RFC2425]:

       CONTACT;ALTREP="CID:part3.msg970930T083000SILVER@example.com":
        Jim Dolittle\, ABC Industries\, +1-919-555-1234

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      The following is an example of this property referencing a network
      resource, such as a vCard [RFC2426] object containing the contact
      information:

       CONTACT;ALTREP="http://example.com/pdi/jdoe.vcf":Jim
         Dolittle\, ABC Industries\, +1-919-555-1234

3.8.4.3.  Organizer

   Property Name:  ORGANIZER

   Purpose:  This property defines the organizer for a calendar
      component.

   Value Type:  CAL-ADDRESS

   Property Parameters:  IANA, non-standard, language, common name,
      directory entry reference, and sent-by property parameters can be
      specified on this property.

   Conformance:  This property MUST be specified in an iCalendar object
      that specifies a group-scheduled calendar entity.  This property
      MUST be specified in an iCalendar object that specifies the
      publication of a calendar user's busy time.  This property MUST
      NOT be specified in an iCalendar object that specifies only a time
      zone definition or that defines calendar components that are not
      group-scheduled components, but are components only on a single
      user's calendar.

   Description:  This property is specified within the "VEVENT",
      "VTODO", and "VJOURNAL" calendar components to specify the
      organizer of a group-scheduled calendar entity.  The property is
      specified within the "VFREEBUSY" calendar component to specify the
      calendar user requesting the free or busy time.  When publishing a
      "VFREEBUSY" calendar component, the property is used to specify
      the calendar that the published busy time came from.

      The property has the property parameters "CN", for specifying the
      common or display name associated with the "Organizer", "DIR", for
      specifying a pointer to the directory information associated with
      the "Organizer", "SENT-BY", for specifying another calendar user
      that is acting on behalf of the "Organizer".  The non-standard
      parameters may also be specified on this property.  If the
      "LANGUAGE" property parameter is specified, the identified
      language applies to the "CN" parameter value.

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   Format Definition:  This property is defined by the following
      notation:

       organizer  = "ORGANIZER" orgparam ":"
                    cal-address CRLF

       orgparam   = *(
                  ;
                  ; The following are OPTIONAL,
                  ; but MUST NOT occur more than once.
                  ;
                  (";" cnparam) / (";" dirparam) / (";" sentbyparam) /
                  (";" languageparam) /
                  ;
                  ; The following is OPTIONAL,
                  ; and MAY occur more than once.
                  ;
                  (";" other-param)
                  ;
                  )

   Example:  The following is an example of this property:

       ORGANIZER;CN=John Smith:mailto:jsmith@example.com

      The following is an example of this property with a pointer to the
      directory information associated with the organizer:

       ORGANIZER;CN=JohnSmith;DIR="ldap://example.com:6666/o=DC%20Ass
        ociates,c=US???(cn=John%20Smith)":mailto:jsmith@example.com

      The following is an example of this property used by another
      calendar user who is acting on behalf of the organizer, with
      responses intended to be sent back to the organizer, not the other
      calendar user:

       ORGANIZER;SENT-BY="mailto:jane_doe@example.com":
        mailto:jsmith@example.com

3.8.4.4.  Recurrence ID

   Property Name:  RECURRENCE-ID

   Purpose:  This property is used in conjunction with the "UID" and
      "SEQUENCE" properties to identify a specific instance of a
      recurring "VEVENT", "VTODO", or "VJOURNAL" calendar component.
      The property value is the original value of the "DTSTART" property
      of the recurrence instance.

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   Value Type:  The default value type is DATE-TIME.  The value type can
      be set to a DATE value type.  This property MUST have the same
      value type as the "DTSTART" property contained within the
      recurring component.  Furthermore, this property MUST be specified
      as a date with local time if and only if the "DTSTART" property
      contained within the recurring component is specified as a date
      with local time.

   Property Parameters:  IANA, non-standard, value data type, time zone
      identifier, and recurrence identifier range parameters can be
      specified on this property.

   Conformance:  This property can be specified in an iCalendar object
      containing a recurring calendar component.

   Description:  The full range of calendar components specified by a
      recurrence set is referenced by referring to just the "UID"
      property value corresponding to the calendar component.  The
      "RECURRENCE-ID" property allows the reference to an individual
      instance within the recurrence set.

      If the value of the "DTSTART" property is a DATE type value, then
      the value MUST be the calendar date for the recurrence instance.

      The DATE-TIME value is set to the time when the original
      recurrence instance would occur; meaning that if the intent is to
      change a Friday meeting to Thursday, the DATE-TIME is still set to
      the original Friday meeting.

      The "RECURRENCE-ID" property is used in conjunction with the "UID"
      and "SEQUENCE" properties to identify a particular instance of a
      recurring event, to-do, or journal.  For a given pair of "UID" and
      "SEQUENCE" property values, the "RECURRENCE-ID" value for a
      recurrence instance is fixed.

      The "RANGE" parameter is used to specify the effective range of
      recurrence instances from the instance specified by the
      "RECURRENCE-ID" property value.  The value for the range parameter
      can only be "THISANDFUTURE" to indicate a range defined by the
      given recurrence instance and all subsequent instances.
      Subsequent instances are determined by their "RECURRENCE-ID" value
      and not their current scheduled start time.  Subsequent instances
      defined in separate components are not impacted by the given
      recurrence instance.  When the given recurrence instance is
      rescheduled, all subsequent instances are also rescheduled by the
      same time difference.  For instance, if the given recurrence
      instance is rescheduled to start 2 hours later, then all
      subsequent instances are also rescheduled 2 hours later.

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      Similarly, if the duration of the given recurrence instance is
      modified, then all subsequence instances are also modified to have
      this same duration.

         Note: The "RANGE" parameter may not be appropriate to
         reschedule specific subsequent instances of complex recurring
         calendar component.  Assuming an unbounded recurring calendar
         component scheduled to occur on Mondays and Wednesdays, the
         "RANGE" parameter could not be used to reschedule only the
         future Monday instances to occur on Tuesday instead.  In such
         cases, the calendar application could simply truncate the
         unbounded recurring calendar component (i.e., with the "COUNT"
         or "UNTIL" rule parts), and create two new unbounded recurring
         calendar components for the future instances.

   Format Definition:  This property is defined by the following
      notation:

       recurid    = "RECURRENCE-ID" ridparam ":" ridval CRLF

       ridparam   = *(
                  ;
                  ; The following are OPTIONAL,
                  ; but MUST NOT occur more than once.
                  ;
                  (";" "VALUE" "=" ("DATE-TIME" / "DATE")) /
                  (";" tzidparam) / (";" rangeparam) /
                  ;
                  ; The following is OPTIONAL,
                  ; and MAY occur more than once.
                  ;
                  (";" other-param)
                  ;
                  )

       ridval     = date-time / date
       ;Value MUST match value type

   Example:  The following are examples of this property:

       RECURRENCE-ID;VALUE=DATE:19960401

       RECURRENCE-ID;RANGE=THISANDFUTURE:19960120T120000Z

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3.8.4.5.  Related To

   Property Name:  RELATED-TO

   Purpose:  This property is used to represent a relationship or
      reference between one calendar component and another.

   Value Type:  TEXT

   Property Parameters:  IANA, non-standard, and relationship type
      property parameters can be specified on this property.

   Conformance:  This property can be specified in the "VEVENT",
      "VTODO", and "VJOURNAL" calendar components.

   Description:  The property value consists of the persistent, globally
      unique identifier of another calendar component.  This value would
      be represented in a calendar component by the "UID" property.

      By default, the property value points to another calendar
      component that has a PARENT relationship to the referencing
      object.  The "RELTYPE" property parameter is used to either
      explicitly state the default PARENT relationship type to the
      referenced calendar component or to override the default PARENT
      relationship type and specify either a CHILD or SIBLING
      relationship.  The PARENT relationship indicates that the calendar
      component is a subordinate of the referenced calendar component.
      The CHILD relationship indicates that the calendar component is a
      superior of the referenced calendar component.  The SIBLING
      relationship indicates that the calendar component is a peer of
      the referenced calendar component.

      Changes to a calendar component referenced by this property can
      have an implicit impact on the related calendar component.  For
      example, if a group event changes its start or end date or time,
      then the related, dependent events will need to have their start
      and end dates changed in a corresponding way.  Similarly, if a
      PARENT calendar component is cancelled or deleted, then there is
      an implied impact to the related CHILD calendar components.  This
      property is intended only to provide information on the
      relationship of calendar components.  It is up to the target
      calendar system to maintain any property implications of this
      relationship.

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   Format Definition:  This property is defined by the following
      notation:

       related    = "RELATED-TO" relparam ":" text CRLF

       relparam   = *(
                  ;
                  ; The following is OPTIONAL,
                  ; but MUST NOT occur more than once.
                  ;
                  (";" reltypeparam) /
                  ;
                  ; The following is OPTIONAL,
                  ; and MAY occur more than once.
                  ;
                  (";" other-param)
                  ;
                  )

      The following is an example of this property:

       RELATED-TO:jsmith.part7.19960817T083000.xyzMail@example.com

       RELATED-TO:19960401-080045-4000F192713-0052@example.com

3.8.4.6.  Uniform Resource Locator

   Property Name:  URL

   Purpose:  This property defines a Uniform Resource Locator (URL)
      associated with the iCalendar object.

   Value Type:  URI

   Property Parameters:  IANA and non-standard property parameters can
      be specified on this property.

   Conformance:  This property can be specified once in the "VEVENT",
      "VTODO", "VJOURNAL", or "VFREEBUSY" calendar components.

   Description:  This property may be used in a calendar component to
      convey a location where a more dynamic rendition of the calendar
      information associated with the calendar component can be found.
      This memo does not attempt to standardize the form of the URI, nor
      the format of the resource pointed to by the property value.  If
      the URL property and Content-Location MIME header are both
      specified, they MUST point to the same resource.

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   Format Definition:  This property is defined by the following
      notation:

       url        = "URL" urlparam ":" uri CRLF

       urlparam   = *(";" other-param)

   Example:  The following is an example of this property:

       URL:http://example.com/pub/calendars/jsmith/mytime.ics

3.8.4.7.  Unique Identifier

   Property Name:  UID

   Purpose:  This property defines the persistent, globally unique
      identifier for the calendar component.

   Value Type:  TEXT

   Property Parameters:  IANA and non-standard property parameters can
      be specified on this property.

   Conformance:  The property MUST be specified in the "VEVENT",
      "VTODO", "VJOURNAL", or "VFREEBUSY" calendar components.

   Description:  The "UID" itself MUST be a globally unique identifier.
      The generator of the identifier MUST guarantee that the identifier
      is unique.  There are several algorithms that can be used to
      accomplish this.  A good method to assure uniqueness is to put the
      domain name or a domain literal IP address of the host on which
      the identifier was created on the right-hand side of an "@", and
      on the left-hand side, put a combination of the current calendar
      date and time of day (i.e., formatted in as a DATE-TIME value)
      along with some other currently unique (perhaps sequential)
      identifier available on the system (for example, a process id
      number).  Using a DATE-TIME value on the left-hand side and a
      domain name or domain literal on the right-hand side makes it
      possible to guarantee uniqueness since no two hosts should be
      using the same domain name or IP address at the same time.  Though
      other algorithms will work, it is RECOMMENDED that the right-hand
      side contain some domain identifier (either of the host itself or
      otherwise) such that the generator of the message identifier can
      guarantee the uniqueness of the left-hand side within the scope of
      that domain.

      This is the method for correlating scheduling messages with the
      referenced "VEVENT", "VTODO", or "VJOURNAL" calendar component.

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      The full range of calendar components specified by a recurrence
      set is referenced by referring to just the "UID" property value
      corresponding to the calendar component.  The "RECURRENCE-ID"
      property allows the reference to an individual instance within the
      recurrence set.

      This property is an important method for group-scheduling
      applications to match requests with later replies, modifications,
      or deletion requests.  Calendaring and scheduling applications
      MUST generate this property in "VEVENT", "VTODO", and "VJOURNAL"
      calendar components to assure interoperability with other group-
      scheduling applications.  This identifier is created by the
      calendar system that generates an iCalendar object.

      Implementations MUST be able to receive and persist values of at
      least 255 octets for this property, but they MUST NOT truncate
      values in the middle of a UTF-8 multi-octet sequence.

   Format Definition:  This property is defined by the following
      notation:

       uid        = "UID" uidparam ":" text CRLF

       uidparam   = *(";" other-param)

   Example:  The following is an example of this property:

       UID:19960401T080045Z-4000F192713-0052@example.com



(page 118 continued on part 6)

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