util_guess_timezone

Tries to match the tzid with a built-in iCal timezone.

Whenever possible, the timezone should be taken from the timezone cache or the VCALENDAR component the owner component belongs to, this should be used just as the last resort when such time zone could not be found.

Parameters:

tzid	a time zone ID

Returns:

matching built-in Timezone for the tzid, or null, when could not be found