TimezoneDSTRule Property

This property defines the recurrence rule for the onset of this daylight savings time observance.

Syntax

property TimezoneDSTRule: String;

Default Value

Remarks

This property defines the recurrence rule for the onset of this daylight savings time observance. Some specific requirements for the usage of TimezoneDSTRule for this purpose include:


FREQ	Frequency of the time zone onset. (Almost always "YEARLY")
BYMONTH	The month of the time zone onset.
BYDAY	The day of the time zone onset. Formatted as a number and a two-character day. "BYDAY=3SU" means the 3rd Sunday of the month. "BYDAY=-1SU" is the last Sunday of the month.
UNTIL	If the observance is known to have an effective end date, the "UNTIL" recurrence rule parameter MUST be used to specify the last valid onset of this observance (i.e., the UNTIL DATE-TIME will be equal to the last instance generated by the recurrence pattern). It MUST be specified in UTC time.

Note that the TimezoneDSTStart and TimezoneDSTOffsetFrom properties must be used when generating the onset DATE-TIME values (instances) from the TimezoneDSTRule

For instance, in the USA Eastern Daylight time before 2007 started on the first Sunday of April. In 2007 Daylight time was changed to begin on the 2nd Sunday in March. Therefore, the UNTIL option should indicate the LAST time this rule will be observed. (2am on April 2nd, 2006). Such a time zone declaration would look like this:

	CalDAV.time zone.DSTName = "EDT"
	CalDAV.time zone.DSTStart = "19870405T020000"
	CalDAV.time zone.DSTOffsetFrom = "-500"
	CalDAV.time zone.DSTOffsetTo = "-400"
	CalDAV.time zone.DSTRule = "FREQ=YEARLY;BYMONTH=4;BYDAY=1SU;UNTIL=20060402T070000Z"

Data Type

String