RFC 2445
Internet Calendaring and Scheduling Core Object Specification (iCalendar)
4.7 Calendar Properties The Calendar Properties are attributes that apply to the iCalendar object, as a whole. These properties do not appear within a calendar component. They SHOULD be specified after the "BEGIN:VCALENDAR" property and prior to any calendar component. 4.7.1 Calendar Scale Property Name: CALSCALE Purpose: This property defines the calendar scale used for the calendar information specified in the iCalendar object.
Value Type: TEXT
Property Parameters: Non-standard property parameters can be
specified on this property.
Conformance: Property can be specified in an iCalendar object. The
default value is "GREGORIAN".
Description: This memo is based on the Gregorian calendar scale. The
Gregorian calendar scale is assumed if this property is not specified
in the iCalendar object. It is expected that other calendar scales
will be defined in other specifications or by future versions of this
memo.
Format Definition: The property is defined by the following notation:
calscale = "CALSCALE" calparam ":" calvalue CRLF
calparam = *(";" xparam)
calvalue = "GREGORIAN" / iana-token
Example: The following is an example of this property:
CALSCALE:GREGORIAN
4.7.2 Method
Property Name: METHOD
Purpose: This property defines the iCalendar object method associated
with the calendar object.
Value Type: TEXT
Property Parameters: Non-standard property parameters can be
specified on this property.
Conformance: The property can be specified in an iCalendar object.
Description: When used in a MIME message entity, the value of this
property MUST be the same as the Content-Type "method" parameter
value. This property can only appear once within the iCalendar
object. If either the "METHOD" property or the Content-Type "method"
parameter is specified, then the other MUST also be specified.
No methods are defined by this specification. This is the subject of
other specifications, such as the iCalendar Transport-independent
Interoperability Protocol (iTIP) defined by [ITIP]. If this property is not present in the iCalendar object, then a scheduling transaction MUST NOT be assumed. In such cases, the iCalendar object is merely being used to transport a snapshot of some calendar information; without the intention of conveying a scheduling semantic. Format Definition: The property is defined by the following notation: method = "METHOD" metparam ":" metvalue CRLF metparam = *(";" xparam) metvalue = iana-token Example: The following is a hypothetical example of this property to convey that the iCalendar object is a request for a meeting: METHOD:REQUEST 4.7.3 Product Identifier Property Name: PRODID Purpose: This property specifies the identifier for the product that created the iCalendar object. Value Type: TEXT Property Parameters: Non-standard property parameters can be specified on this property. Conformance: The property MUST be specified once in an iCalendar object. Description: The vendor of the implementation SHOULD assure that this is a globally unique identifier; using some technique such as an FPI value, as defined in [ISO 9070]. This property SHOULD not be used to alter the interpretation of an iCalendar object beyond the semantics specified in this memo. For example, it is not to be used to further the understanding of non- standard properties. Format Definition: The property is defined by the following notation: prodid = "PRODID" pidparam ":" pidvalue CRLF
pidparam = *(";" xparam)
pidvalue = text
;Any text that describes the product and version
;and that is generally assured of being unique.
Example: The following is an example of this property. It does not
imply that English is the default language.
PRODID:-//ABC Corporation//NONSGML My Product//EN
4.7.4 Version
Property Name: VERSION
Purpose: This property specifies the identifier corresponding to the
highest version number or the minimum and maximum range of the
iCalendar specification that is required in order to interpret the
iCalendar object.
Value Type: TEXT
Property Parameters: Non-standard property parameters can be
specified on this property.
Conformance: This property MUST be specified by an iCalendar object,
but MUST only be specified once.
Description: A value of "2.0" corresponds to this memo.
Format Definition: The property is defined by the following notation:
version = "VERSION" verparam ":" vervalue CRLF
verparam = *(";" xparam)
vervalue = "2.0" ;This memo
/ maxver
/ (minver ";" maxver)
minver = <A IANA registered iCalendar version identifier>
;Minimum iCalendar version needed to parse the iCalendar object
maxver = <A IANA registered iCalendar version identifier>
;Maximum iCalendar version needed to parse the iCalendar object
Example: The following is an example of this property:
VERSION:2.0
4.8 Component Properties
The following properties can appear within calendar components, as
specified by each component property definition.
4.8.1 Descriptive Component Properties
The following properties specify descriptive information about
calendar components.
4.8.1.1 Attachment
Property Name: ATTACH
Purpose: The property provides the capability to associate a document
object with a calendar component.
Value Type: The default value type for this property is URI. The
value type can also be set to BINARY to indicate inline binary
encoded content information.
Property Parameters: Non-standard, inline encoding, format type and
value data type property parameters can be specified on this
property.
Conformance: The property can be specified in a "VEVENT", "VTODO",
"VJOURNAL" or "VALARM" calendar components.
Description: The property can be specified within "VEVENT", "VTODO",
"VJOURNAL", or "VALARM" calendar components. This property can be
specified multiple times within an iCalendar object.
Format Definition: The property is defined by the following notation:
attach = "ATTACH" attparam ":" uri CRLF
attach =/ "ATTACH" attparam ";" "ENCODING" "=" "BASE64"
";" "VALUE" "=" "BINARY" ":" binary
attparam = *(
; the following is optional,
; but MUST NOT occur more than once
(";" fmttypeparam) /
; the following is optional,
; and MAY occur more than once
(";" xparam)
)
Example: The following are examples of this property:
ATTACH:CID:jsmith.part3.960817T083000.xyzMail@host1.com
ATTACH;FMTTYPE=application/postscript:ftp://xyzCorp.com/pub/
reports/r-960812.ps
4.8.1.2 Categories
Property Name: CATEGORIES
Purpose: This property defines the categories for a calendar
component.
Value Type: TEXT
Property Parameters: Non-standard and language property parameters
can be specified on this property.
Conformance: The property can be specified within "VEVENT", "VTODO"
or "VJOURNAL" calendar components.
Description: This property is used to specify categories or subtypes
of the calendar component. The categories are useful in searching for
a calendar component of a particular type and category. Within the
"VEVENT", "VTODO" or "VJOURNAL" calendar components, more than one
category can be specified as a list of categories separated by the
COMMA character (US-ASCII decimal 44).
Format Definition: The property is defined by the following notation:
categories = "CATEGORIES" catparam ":" text *("," text)
CRLF
catparam = *(
; the following is optional,
; but MUST NOT occur more than once
(";" languageparam ) /
; the following is optional,
; and MAY occur more than once
(";" xparam)
)
Example: The following are examples of this property:
CATEGORIES:APPOINTMENT,EDUCATION
CATEGORIES:MEETING
4.8.1.3 Classification
Property Name: CLASS
Purpose: This property defines the access classification for a
calendar component.
Value Type: TEXT
Property Parameters: Non-standard property parameters can be
specified on this property.
Conformance: The property can be specified once in a "VEVENT",
"VTODO" or "VJOURNAL" calendar components.
Description: An access classification is only one component of the
general security system within a calendar application. It provides a
method of capturing the scope of the access the calendar owner
intends for information within an individual calendar entry. The
access classification of an individual iCalendar component is useful
when measured along with the other security components of a calendar
system (e.g., calendar user authentication, authorization, access
rights, access role, etc.). Hence, the semantics of the individual
access classifications cannot be completely defined by this memo
alone. Additionally, due to the "blind" nature of most exchange
processes using this memo, these access classifications cannot serve
as an enforcement statement for a system receiving an iCalendar
object. Rather, they provide a method for capturing the intention of
the calendar owner for the access to the calendar component.
Format Definition: The property is defined by the following notation:
class = "CLASS" classparam ":" classvalue CRLF
classparam = *(";" xparam)
classvalue = "PUBLIC" / "PRIVATE" / "CONFIDENTIAL" / iana-token
/ x-name
;Default is PUBLIC
Example: The following is an example of this property:
CLASS:PUBLIC
4.8.1.4 Comment
Property Name: COMMENT
Purpose: This property specifies non-processing information intended
to provide a comment to the calendar user.
Value Type: TEXT
Property Parameters: Non-standard, alternate text representation and
language property parameters can be specified on this property.
Conformance: This property can be specified in "VEVENT", "VTODO",
"VJOURNAL", "VTIMEZONE" or "VFREEBUSY" calendar components.
Description: The property can be specified multiple times.
Format Definition: The property is defined by the following notation:
comment = "COMMENT" commparam ":" text CRLF
commparam = *(
; the following are optional,
; but MUST NOT occur more than once
(";" altrepparam) / (";" languageparam) /
; the following is optional,
; and MAY occur more than once
(";" xparam)
)
Example: The following is an example of this property:
COMMENT:The meeting really needs to include both ourselves
and the customer. We can't hold this meeting without them.
As a matter of fact\, the venue for the meeting ought to be at
their site. - - John
The data type for this property is TEXT.
4.8.1.5 Description
Property Name: DESCRIPTION
Purpose: This property provides a more complete description of the
calendar component, than that provided by the "SUMMARY" property.
Value Type: TEXT
Property Parameters: Non-standard, alternate text representation and
language property parameters can be specified on this property.
Conformance: The property can be specified in the "VEVENT", "VTODO",
"VJOURNAL" or "VALARM" calendar components. The property can be
specified multiple times only within a "VJOURNAL" calendar component.
Description: This property is used in the "VEVENT" and "VTODO" to
capture lengthy textual decriptions associated with the activity.
This property is used in the "VJOURNAL" calendar component to capture
one more textual journal entries.
This property is used in the "VALARM" calendar component to capture
the display text for a DISPLAY category of alarm, to capture the body
text for an EMAIL category of alarm and to capture the argument
string for a PROCEDURE category of alarm.
Format Definition: The property is defined by the following notation:
description = "DESCRIPTION" descparam ":" text CRLF
descparam = *(
; the following are optional,
; but MUST NOT occur more than once
(";" altrepparam) / (";" languageparam) /
; the following is optional,
; and MAY occur more than once
(";" xparam)
)
Example: The following is an example of the property with formatted
line breaks in the property value:
DESCRIPTION:Meeting to provide technical review for "Phoenix"
design.\n Happy Face Conference Room. Phoenix design team
MUST attend this meeting.\n RSVP to team leader.
The following is an example of the property with folding of long
lines:
DESCRIPTION:Last draft of the new novel is to be completed
for the editor's proof today.
4.8.1.6 Geographic Position
Property Name: GEO
Purpose: This property specifies information related to the global
position for the activity specified by a calendar component.
Value Type: FLOAT. The value MUST be two SEMICOLON separated FLOAT
values.
Property Parameters: Non-standard property parameters can be
specified on this property.
Conformance: This property can be specified in "VEVENT" or "VTODO"
calendar components.
Description: The property value specifies latitude and longitude, in
that order (i.e., "LAT LON" ordering). The longitude represents the
location east or west of the prime meridian as a positive or negative
real number, respectively. The longitude and latitude values MAY be
specified up to six decimal places, which will allow for accuracy to
within one meter of geographical position. Receiving applications
MUST accept values of this precision and MAY truncate values of
greater precision.
Values for latitude and longitude shall be expressed as decimal
fractions of degrees. Whole degrees of latitude shall be represented
by a two-digit decimal number ranging from 0 through 90. Whole
degrees of longitude shall be represented by a decimal number ranging
from 0 through 180. When a decimal fraction of a degree is specified,
it shall be separated from the whole number of degrees by a decimal
point.
Latitudes north of the equator shall be specified by a plus sign (+),
or by the absence of a minus sign (-), preceding the digits
designating degrees. Latitudes south of the Equator shall be
designated by a minus sign (-) preceding the digits designating
degrees. A point on the Equator shall be assigned to the Northern
Hemisphere.
Longitudes east of the prime meridian shall be specified by a plus
sign (+), or by the absence of a minus sign (-), preceding the digits
designating degrees. Longitudes west of the meridian shall be
designated by minus sign (-) preceding the digits designating
degrees. A point on the prime meridian shall be assigned to the
Eastern Hemisphere. A point on the 180th meridian shall be assigned
to the Western Hemisphere. One exception to this last convention is
permitted. For the special condition of describing a band of latitude
around the earth, the East Bounding Coordinate data element shall be
assigned the value +180 (180) degrees.
Any spatial address with a latitude of +90 (90) or -90 degrees will
specify the position at the North or South Pole, respectively. The
component for longitude may have any legal value.
With the exception of the special condition described above, this
form is specified in Department of Commerce, 1986, Representation of
geographic point locations for information interchange (Federal
Information Processing Standard 70-1): Washington, Department of
Commerce, National Institute of Standards and Technology.
The simple formula for converting degrees-minutes-seconds into
decimal degrees is:
decimal = degrees + minutes/60 + seconds/3600.
Format Definition: The property is defined by the following notation:
geo = "GEO" geoparam ":" geovalue CRLF
geoparam = *(";" xparam)
geovalue = float ";" float
;Latitude and Longitude components
Example: The following is an example of this property:
GEO:37.386013;-122.082932
4.8.1.7 Location Property Name: LOCATION Purpose: The property defines the intended venue for the activity defined by a calendar component. Value Type: TEXT Property Parameters: Non-standard, alternate text representation and language property parameters can be specified on this property. Conformance: This property can be specified in "VEVENT" or "VTODO" calendar component. Description: Specific venues such as conference or meeting rooms may be explicitly specified using this property. An alternate representation may be specified that is a URI that points to directory information with more structured specification of the location. For example, the alternate representation may specify either an LDAP URI pointing to an LDAP server entry or a CID URI pointing to a MIME body part containing a vCard [RFC 2426] for the location. Format Definition: The property is defined by the following notation: location = "LOCATION locparam ":" text CRLF locparam = *( ; the following are optional, ; but MUST NOT occur more than once (";" altrepparam) / (";" languageparam) / ; the following is optional, ; and MAY occur more than once (";" xparam) ) Example: The following are some examples of this property: LOCATION:Conference Room - F123, Bldg. 002 LOCATION;ALTREP="http://xyzcorp.com/conf-rooms/f123.vcf": Conference Room - F123, Bldg. 002
4.8.1.8 Percent Complete Property Name: PERCENT-COMPLETE Purpose: This property is used by an assignee or delegatee of a to-do to convey the percent completion of a to-do to the Organizer. Value Type: INTEGER Property Parameters: Non-standard property parameters can be specified on this property. Conformance: This property can be specified in a "VTODO" calendar component. Description: The property value is a positive integer between zero and one hundred. A value of "0" indicates the to-do has not yet been started. A value of "100" indicates that the to-do has been completed. Integer values in between indicate the percent partially complete. When a to-do is assigned to multiple individuals, the property value indicates the percent complete for that portion of the to-do assigned to the assignee or delegatee. For example, if a to-do is assigned to both individuals "A" and "B". A reply from "A" with a percent complete of "70" indicates that "A" has completed 70% of the to-do assigned to them. A reply from "B" with a percent complete of "50" indicates "B" has completed 50% of the to-do assigned to them. Format Definition: The property is defined by the following notation: percent = "PERCENT-COMPLETE" pctparam ":" integer CRLF pctparam = *(";" xparam) Example: The following is an example of this property to show 39% completion: PERCENT-COMPLETE:39 4.8.1.9 Priority Property Name: PRIORITY Purpose: The property defines the relative priority for a calendar component. Value Type: INTEGER
Property Parameters: Non-standard property parameters can be
specified on this property.
Conformance: The property can be specified in a "VEVENT" or "VTODO"
calendar component.
Description: The priority is specified as an integer in the range
zero to nine. A value of zero (US-ASCII decimal 48) specifies an
undefined priority. A value of one (US-ASCII decimal 49) is the
highest priority. A value of two (US-ASCII decimal 50) is the second
highest priority. Subsequent numbers specify a decreasing ordinal
priority. A value of nine (US-ASCII decimal 58) is the lowest
priority.
A CUA with a three-level priority scheme of "HIGH", "MEDIUM" and
"LOW" is mapped into this property such that a property value in the
range of one (US-ASCII decimal 49) to four (US-ASCII decimal 52)
specifies "HIGH" priority. A value of five (US-ASCII decimal 53) is
the normal or "MEDIUM" priority. A value in the range of six (US-
ASCII decimal 54) to nine (US-ASCII decimal 58) is "LOW" priority.
A CUA with a priority schema of "A1", "A2", "A3", "B1", "B2", ...,
"C3" is mapped into this property such that a property value of one
(US-ASCII decimal 49) specifies "A1", a property value of two (US-
ASCII decimal 50) specifies "A2", a property value of three (US-ASCII
decimal 51) specifies "A3", and so forth up to a property value of 9
(US-ASCII decimal 58) specifies "C3".
Other integer values are reserved for future use.
Within a "VEVENT" calendar component, this property specifies a
priority for the event. This property may be useful when more than
one event is scheduled for a given time period.
Within a "VTODO" calendar component, this property specified a
priority for the to-do. This property is useful in prioritizing
multiple action items for a given time period.
Format Definition: The property is specified by the following
notation:
priority = "PRIORITY" prioparam ":" privalue CRLF
;Default is zero
prioparam = *(";" xparam)
privalue = integer ;Must be in the range [0..9]
; All other values are reserved for future use
The following is an example of a property with the highest priority:
PRIORITY:1
The following is an example of a property with a next highest
priority:
PRIORITY:2
Example: The following is an example of a property with no priority.
This is equivalent to not specifying the "PRIORITY" property:
PRIORITY:0
4.8.1.10 Resources
Property Name: RESOURCES
Purpose: This property defines the equipment or resources anticipated
for an activity specified by a calendar entity..
Value Type: TEXT
Property Parameters: Non-standard, alternate text representation and
language property parameters can be specified on this property.
Conformance: This property can be specified in "VEVENT" or "VTODO"
calendar component.
Description: The property value is an arbitrary text. More than one
resource can be specified as a list of resources separated by the
COMMA character (US-ASCII decimal 44).
Format Definition: The property is defined by the following notation:
resources = "RESOURCES" resrcparam ":" text *("," text) CRLF
resrcparam = *(
; the following are optional,
; but MUST NOT occur more than once
(";" altrepparam) / (";" languageparam) /
; the following is optional,
; and MAY occur more than once
(";" xparam)
)
Example: The following is an example of this property:
RESOURCES:EASEL,PROJECTOR,VCR
RESOURCES;LANGUAGE=fr:1 raton-laveur
4.8.1.11 Status
Property Name: STATUS
Purpose: This property defines the overall status or confirmation for
the calendar component.
Value Type: TEXT
Property Parameters: Non-standard property parameters can be
specified on this property.
Conformance: This property can be specified in "VEVENT", "VTODO" or
"VJOURNAL" calendar components.
Description: In a group scheduled calendar component, the property is
used by the "Organizer" to provide a confirmation of the event to the
"Attendees". For example in a "VEVENT" calendar component, the
"Organizer" can indicate that a meeting is tentative, confirmed or
cancelled. In a "VTODO" calendar component, the "Organizer" can
indicate that an action item needs action, is completed, is in
process or being worked on, or has been cancelled. In a "VJOURNAL"
calendar component, the "Organizer" can indicate that a journal entry
is draft, final or has been cancelled or removed.
Format Definition: The property is defined by the following notation:
status = "STATUS" statparam] ":" statvalue CRLF
statparam = *(";" xparam)
statvalue = "TENTATIVE" ;Indicates event is
;tentative.
/ "CONFIRMED" ;Indicates event is
;definite.
/ "CANCELLED" ;Indicates event was
;cancelled.
;Status values for a "VEVENT"
statvalue =/ "NEEDS-ACTION" ;Indicates to-do needs action.
/ "COMPLETED" ;Indicates to-do completed.
/ "IN-PROCESS" ;Indicates to-do in process of
/ "CANCELLED" ;Indicates to-do was cancelled.
;Status values for "VTODO".
statvalue =/ "DRAFT" ;Indicates journal is draft.
/ "FINAL" ;Indicates journal is final.
/ "CANCELLED" ;Indicates journal is removed.
;Status values for "VJOURNAL".
Example: The following is an example of this property for a "VEVENT"
calendar component:
STATUS:TENTATIVE
The following is an example of this property for a "VTODO" calendar
component:
STATUS:NEEDS-ACTION
The following is an example of this property for a "VJOURNAL"
calendar component:
STATUS:DRAFT
4.8.1.12 Summary
Property Name: SUMMARY
Purpose: This property defines a short summary or subject for the
calendar component.
Value Type: TEXT
Property Parameters: Non-standard, alternate text representation and
language property parameters can be specified on this property.
Conformance: The property can be specified in "VEVENT", "VTODO",
"VJOURNAL" or "VALARM" calendar components.
Description: This property is used in the "VEVENT", "VTODO" and
"VJOURNAL" calendar components to capture a short, one line summary
about the activity or journal entry.
This property is used in the "VALARM" calendar component to capture
the subject of an EMAIL category of alarm.
Format Definition: The property is defined by the following notation:
summary = "SUMMARY" summparam ":" text CRLF
summparam = *(
; the following are optional,
; but MUST NOT occur more than once
(";" altrepparam) / (";" languageparam) /
; the following is optional,
; and MAY occur more than once
(";" xparam)
)
Example: The following is an example of this property:
SUMMARY:Department Party
4.8.2 Date and Time Component Properties
The following properties specify date and time related information in
calendar components.
4.8.2.1 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: Non-standard property parameters can be
specified on this property.
Conformance: The property can be specified in a "VTODO" calendar
component.
Description: The date and time MUST be in a UTC format.
Format Definition: The property is defined by the following notation:
completed = "COMPLETED" compparam ":" date-time CRLF
compparam = *(";" xparam)
Example: The following is an example of this property:
COMPLETED:19960401T235959Z
4.8.2.2 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: Non-standard, value data type, 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 MUST be
later in time than the value of the "DTSTART" property.
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: The property is defined by the following notation:
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
(";" xparam)
)
dtendval = date-time / date
;Value MUST match value type
Example: The following is an example of this property:
DTEND:19960401T235959Z
DTEND;VALUE=DATE:19980704
4.8.2.3 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: Non-standard, value data type, time zone
identifier property parameters can be specified on this property.
Conformance: The property can be specified once in a "VTODO" calendar
component.
Description: The value MUST be a date/time equal to or after the
DTSTART value, if specified.
Format Definition: The 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
*(";" xparam)
)
dueval = date-time / date
;Value MUST match value type
Example: The following is an example of this property:
DUE:19980430T235959Z
4.8.2.4 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: Non-standard, value data type, time zone
identifier property parameters can be specified on this property.
Conformance: This property can be specified in the "VEVENT", "VTODO",
"VFREEBUSY", or "VTIMEZONE" calendar components.
Description: Within the "VEVENT" calendar component, this property
defines the start date and time for the event. The property is
REQUIRED in "VEVENT" calendar components. Events can have a start
date/time but no end date/time. In that case, the event does not take
up any time.
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 "VTIMEZONE" calendar component, this property defines the
effective start date and time for a time zone specification. This
property is REQUIRED within each STANDARD and DAYLIGHT part included
in "VTIMEZONE" calendar components and MUST be specified as a local
DATE-TIME without the "TZID" property parameter.
Format Definition: The 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
*(";" xparam)
)
dtstval = date-time / date
;Value MUST match value type
Example: The following is an example of this property:
DTSTART:19980118T073000Z
4.8.2.5 Duration
Property Name: DURATION
Purpose: The property specifies a positive duration of time.
Value Type: DURATION
Property Parameters: Non-standard property parameters can be
specified on this property.
Conformance: The property can be specified in "VEVENT", "VTODO",
"VFREEBUSY" 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 "VFREEBUSY" calendar component the property may be
used to specify the interval of free time being requested. In a
"VALARM" calendar component the property may be used to specify the
delay period prior to repeating an alarm.
Format Definition: The property is defined by the following notation:
duration = "DURATION" durparam ":" dur-value CRLF
;consisting of a positive duration of time.
durparam = *(";" xparam)
Example: The following is an example of this property that specifies
an interval of time of 1 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
4.8.2.6 Free/Busy Time
Property Name: FREEBUSY
Purpose: The property defines one or more free or busy time
intervals.
Value Type: PERIOD. The date and time values MUST be in an UTC time
format.
Property Parameters: Non-standard or free/busy time type property
parameters can be specified on this property.
Conformance: The property can be specified in a "VFREEBUSY" calendar
component.
Property Parameter: "FBTYPE" and non-standard parameters can be
specified on this property.
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 (US-ASCII decimal 44). In such cases, the
"FREEBUSY" property values SHOULD 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: The 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
(";" xparam)
)
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
4.8.2.7 Time Transparency
Property Name: TRANSP
Purpose: This property defines whether an event is transparent or not
to busy time searches.
Value Type: TEXT
Property Parameters: 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: The property is specified by the following
notation:
transp = "TRANSP" tranparam ":" transvalue CRLF
tranparam = *(";" xparam)
transvalue = "OPAQUE" ;Blocks or opaque on busy time searches.
/ "TRANSPARENT" ;Transparent on busy time searches.
;Default value is OPAQUE
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
4.8.3 Time Zone Component Properties
The following properties specify time zone information in calendar
components.
4.8.3.1 Time Zone Identifier
Property Name: TZID
Purpose: This property specifies the text value that uniquely
identifies the "VTIMEZONE" calendar component.
Value Type: TEXT
Property Parameters: 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 data type
is either DATE-TIME or TIME and not intended to specify a UTC or a
"floating" time. The presence of the SOLIDUS character (US-ASCII
decimal 47) 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 Olson database [TZ]. The specification of
globally unique time zone identifiers is not addressed by this
document and is left for future study.
Format Definition: This property is defined by the following
notation:
tzid = "TZID" tzidpropparam ":" [tzidprefix] text CRLF
tzidpropparam = *(";" xparam)
;tzidprefix = "/"
; Defined previously. Just listed here for reader convenience.
Example: The following are examples of non-globally unique time zone
identifiers:
TZID:US-Eastern
TZID:California-Los_Angeles
The following is an example of a fictitious globally unique time zone
identifier:
TZID:/US-New_York-New_York
4.8.3.2 Time Zone Name
Property Name: TZNAME
Purpose: This property specifies the customary designation for a time
zone description.
Value Type: TEXT
Property Parameters: Non-standard and language property parameters
can be specified on this property.
Conformance: This property can be specified in a "VTIMEZONE" calendar
component.
Description: This property may be specified in multiple languages; in
order to provide for different language requirements.
Format Definition: This property is defined by the following
notation:
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
(";" xparam)
)
Example: The following are example of this property:
TZNAME:EST
The following is an example of this property when two different
languages for the time zone name are specified:
TZNAME;LANGUAGE=en:EST
TZNAME;LANGUAGE=fr-CA:HNE
4.8.3.3 Time Zone Offset From
Property Name: TZOFFSETFROM
Purpose: This property specifies the offset which is in use prior to
this time zone observance.
Value Type: UTC-OFFSET
Property Parameters: Non-standard property parameters can be
specified on this property.
Conformance: This property MUST be specified in a "VTIMEZONE"
calendar component.
Description: This property specifies the offset which 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.
Format Definition: The property is defined by the following notation:
tzoffsetfrom = "TZOFFSETFROM" frmparam ":" utc-offset
CRLF
frmparam = *(";" xparam)
Example: The following are examples of this property:
TZOFFSETFROM:-0500
TZOFFSETFROM:+1345
4.8.3.4 Time Zone Offset To
Property Name: TZOFFSETTO
Purpose: This property specifies the offset which is in use in this
time zone observance.
Value Type: UTC-OFFSET
Property Parameters: Non-standard property parameters can be
specified on this property.
Conformance: This property MUST be specified in a "VTIMEZONE"
calendar component.
Description: This property specifies the offset which 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: The property is defined by the following notation:
tzoffsetto = "TZOFFSETTO" toparam ":" utc-offset CRLF
toparam = *(";" xparam)
Example: The following are examples of this property:
TZOFFSETTO:-0400
TZOFFSETTO:+1245
4.8.3.5 Time Zone URL
Property Name: TZURL
Purpose: The TZURL 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: Non-standard property parameters can be
specified on this property.
Conformance: This property can be specified in a "VTIMEZONE" calendar
component.
Description: The TZURL 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: The property is defined by the following notation:
tzurl = "TZURL" tzurlparam ":" uri CRLF
tzurlparam = *(";" xparam)
Example: The following is an example of this property:
TZURL:http://timezones.r.us.net/tz/US-California-Los_Angeles
4.8.4 Relationship Component Properties The following properties specify relationship information in calendar components. 4.8.4.1 Attendee Property Name: ATTENDEE Purpose: The property defines an "Attendee" within a calendar component. Value Type: CAL-ADDRESS Property Parameters: 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 entities that are not group scheduled entities, but are entities only on a single user's calendar. Description: The 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 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: The 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
(";" xparam)
)
Example: The following are examples of this property's use for a to-
do:
ORGANIZER:MAILTO:jsmith@host1.com
ATTENDEE;MEMBER="MAILTO:DEV-GROUP@host2.com":
MAILTO:joecool@host2.com
ATTENDEE;DELEGATED-FROM="MAILTO:immud@host3.com":
MAILTO:ildoit@host1.com
The following is an example of this property used for specifying
multiple attendees to an event:
ORGANIZER:MAILTO:jsmith@host1.com
ATTENDEE;ROLE=REQ-PARTICIPANT;PARTSTAT=TENTATIVE;CN=Henry Cabot
:MAILTO:hcabot@host2.com
ATTENDEE;ROLE=REQ-PARTICIPANT;DELEGATED-FROM="MAILTO:bob@host.com"
;PARTSTAT=ACCEPTED;CN=Jane Doe:MAILTO:jdoe@host1.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://host.com:6666/o=eDABC%
20Industries,c=3DUS??(cn=3DBJim%20Dolittle)":MAILTO:jimdo@
host1.com
The following is an example of this property with "delegatee" and
"delegator" information for an event:
ORGANIZER;CN=John Smith:MAILTO:jsmith@host.com
ATTENDEE;ROLE=REQ-PARTICIPANT;PARTSTAT=TENTATIVE;DELEGATED-FROM=
"MAILTO:iamboss@host2.com";CN=Henry Cabot:MAILTO:hcabot@
host2.com
ATTENDEE;ROLE=NON-PARTICIPANT;PARTSTAT=DELEGATED;DELEGATED-TO=
"MAILTO:hcabot@host2.com";CN=The Big Cheese:MAILTO:iamboss
@host2.com
ATTENDEE;ROLE=REQ-PARTICIPANT;PARTSTAT=ACCEPTED;CN=Jane Doe
:MAILTO:jdoe@host1.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@host1.com;CN=John Smith:MAILTO:
jsmith@host1.com
4.8.4.2 Contact
Property Name: CONTACT
Purpose: The property is used to represent contact information or
alternately a reference to contact information associated with the
calendar component.
Value Type: TEXT
Property Parameters: Non-standard, alternate text representation and
language property parameters can be specified on this property.
Conformance: The 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 [RFC 2426], for the contact information. Format Definition: The 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 (";" xparam) ) 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 a LDAP URI to a directory entry containing the contact information: CONTACT;ALTREP="ldap://host.com:6666/o=3DABC%20Industries\, c=3DUS??(cn=3DBJim%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 [RFC 2426] embedded in a [MIME-DIR] content-type: CONTACT;ALTREP="CID=<part3.msg970930T083000SILVER@host.com>":Jim Dolittle\, ABC Industries\, +1-919-555-1234 The following is an example of this property referencing a network resource, such as a vCard [RFC 2426] object containing the contact information:
CONTACT;ALTREP="http://host.com/pdi/jdoe.vcf":Jim
Dolittle\, ABC Industries\, +1-919-555-1234
4.8.4.3 Organizer
Property Name: ORGANIZER
Purpose: The property defines the organizer for a calendar component.
Value Type: CAL-ADDRESS
Property Parameters: Non-standard, language, common name, directory
entry reference, 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 entities that are not group scheduled entities,
but are entities only on a single user's calendar.
Description: The property is specified within the "VEVENT", "VTODO",
"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.
Format Definition: The 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
(";" xparam)
)
Example: The following is an example of this property:
ORGANIZER;CN=John Smith:MAILTO:jsmith@host1.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://host.com:6666/o=3DDC%20Associ
ates,c=3DUS??(cn=3DJohn%20Smith)":MAILTO:jsmith@host1.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@host.com":
MAILTO:jsmith@host1.com
4.8.4.4 Recurrence ID
Property Name: RECURRENCE-ID
Purpose: This property is used in conjunction with the "UID" and
"SEQUENCE" property to identify a specific instance of a recurring
"VEVENT", "VTODO" or "VJOURNAL" calendar component. The property
value is the effective value of the "DTSTART" property of the
recurrence instance.
Value Type: The default value type for this property is DATE-TIME.
The time format can be any of the valid forms defined for a DATE-TIME
value type. See DATE-TIME value type definition for specific
interpretations of the various forms. The value type can be set to
DATE.
Property Parameters: Non-standard property, 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" property 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. When the definition of the recurrence
set for a calendar component changes, and hence the "SEQUENCE"
property value changes, the "RECURRENCE-ID" for a given recurrence
instance might also change.The "RANGE" parameter is used to specify
the effective range of recurrence instances from the instance
specified by the "RECURRENCE-ID" property value. The default value
for the range parameter is the single recurrence instance only. The
value can also be "THISANDPRIOR" to indicate a range defined by the
given recurrence instance and all prior instances or the value can be
"THISANDFUTURE" to indicate a range defined by the given recurrence
instance and all subsequent instances.
Format Definition: The 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
(";" xparam)
)
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
4.8.4.5 Related To
Property Name: RELATED-TO
Purpose: The property is used to represent a relationship or
reference between one calendar component and another.
Value Type: TEXT
Property Parameters: Non-standard and relationship type property
parameters can be specified on this property.
Conformance: The property can be specified one or more times in the
"VEVENT", "VTODO" or "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 canceled 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.
Format Definition: The 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
(";" xparm)
)
The following is an example of this property:
RELATED-TO:<jsmith.part7.19960817T083000.xyzMail@host3.com>
RELATED-TO:<19960401-080045-4000F192713-0052@host1.com>
4.8.4.6 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: 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.
Format Definition: The property is defined by the following notation:
url = "URL" urlparam ":" uri CRLF
urlparam = *(";" xparam)
Example: The following is an example of this property:
URL:http://abc.com/pub/calendars/jsmith/mytime.ics
4.8.4.7 Unique Identifier
Property Name: UID
Purpose: This property defines the persistent, globally unique
identifier for the calendar component.
Value Type: TEXT
Property Parameters: 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. The identifier is RECOMMENDED to be the identical syntax to the
[RFC 822] addr-spec. 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 the "@", 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.
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 characters for this property.
Format Definition: The property is defined by the following notation:
uid = "UID" uidparam ":" text CRLF
uidparam = *(";" xparam)
Example: The following is an example of this property:
UID:19960401T080045Z-4000F192713-0052@host1.com
(page 112 continued on part 4)
