Returns True if daylight saving is currently in effect at the specified time (or now) in the specified time zone (or the program's time zone).

If Val is a Long value, it is the index value of a time zone defined in the registry on the server.

If Val is a Text value, it is the name of a time zone defined in the registry on the server.

If Val is omitted, NULL or empty, the time zone associated with the program in which the function is called is used. By default, the program’s time zone is the local time zone of the server, but this can be changed by calling SetTimeZone.

If a time zone name is used, it is case-insensitive.

The special values of -1 and “UTC” can be used for the time zone; these do not correspond to anything in the registry, but instead refer to UTC time, with no offset or daylight saving defined.

If Val is any other type, an error occurs. If the time zone specified by Val cannot be found in the registry, an error occurs.

If Time is omitted, or equal to 30 December 1899, 00:00:00 (the date internally represented by the numeric value 0), then the current local date and time for the time zone are used.

For some time zones (for example, 275 “West Pacific Standard Time”) this function always returns False, because the time zone does not use daylight saving.

This example returns True if daylight-saving is in effect for the current local date and time in the Central Standard Time time zone.