4.3.5 Date-Time

Basic Definition | Formal Definition | Description| Example

Basic Definition

Value Name
This value type is used to identify values that specify a precise calendar date and time of day.

Formal Definition

The value type is defined by the following

  date-time  = date "T" time ;As specified in the date and time
                             ;value definitions


If the property permits, multiple "date-time" values are specified as a COMMA character (US-ASCII decimal 44) separated list of values. No additional content value encoding (i.e., BACKSLASH character encoding) is defined for this value type.

The "DATE-TIME" data type is used to identify values that contain a precise calendar date and time of day. The format is based on the [ISO 8601] complete representation, basic format for a calendar date and time of day. The text format is a concatenation of the "date", followed by the LATIN CAPITAL LETTER T character (US-ASCII decimal 84) time designator, followed by the "time" format.

The "DATE-TIME" data type expresses time values in three forms:

The form of date and time with UTC offset MUST NOT be used. For example, the following is not valid for a date-time value: DTSTART:19980119T230000-0800 ;Invalid time format


The date with local time form is simply a date-time value that does not contain the UTC designator nor does it reference a time zone. For example, the following represents Janurary 18, 1998, at 11 PM:


Date-time values of this type are said to be "floating" and are not bound to any time zone in particular. They are used to represent the same hour, minute, and second value regardless of which time zone is currently being observed. For example, an event can be defined that indicates that an individual will be busy from 11:00 AM to 1:00 PM every day, no matter which time zone the person is in. In these cases, a local time can be specified. The recipient of an iCalendar object with a property value consisting of a local time, without any relative time zone information, SHOULD interpret the value as being fixed to whatever time zone the ATTENDEE is in at any given moment. This means that two ATTENDEEs, in different time zones, receiving the same event definition as a floating time, may be participating in the event at different actual times. Floating time SHOULD only be used where that is the reasonable behavior.

In most cases, a fixed time is desired. To properly communicate a fixed time in a property value, either UTC time or local time with time zone reference MUST be specified.

The use of local time in a DATE-TIME value without the TZID property parameter is to be interpreted as floating time, regardless of the existence of "VTIMEZONE" calendar components in the iCalendar object.


The date with UTC time, or absolute time, is identified by a LATIN CAPITAL LETTER Z suffix character (US-ASCII decimal 90), the UTC designator, appended to the time value. For example, the following represents January 19, 1998, at 0700 UTC:


The TZID property parameter MUST NOT be applied to DATE-TIME properties whose time values are specified in UTC.


The date and local time with reference to time zone information is identified by the use the TZID property parameter to reference the appropriate time zone definition. TZID is discussed in detail in the section on Time Zone. For example, the following represents 2 AM in New York on Janurary 19, 1998:



The following represents July 14, 1997, at 1:30 PM in New
York City in each of the three time formats, using the "DTSTART"

  DTSTART:19970714T133000            ;Local time
  DTSTART:19970714T173000Z           ;UTC time
  DTSTART;TZID=US-Eastern:19970714T133000    ;Local time and time
                     ; zone reference

A time value MUST ONLY specify 60 seconds when specifying the
periodic "leap second" in the time value. For example: