Subject: [Ietf-calsify] Exchange and new timezones

From: jeffrey at osafoundation.org (Jeffrey Harris)
Date: Thu Feb 15 13:14:16 2007

Hi Folks,

I thought I'd mention to other folks an issue with the way
Exchange/Outlook are dealing with the new US timezones.

Here's the VTIMEZONE Outlook serialized for a US/Eastern recurring event
starting in mid-2006:

BEGIN:VTIMEZONE
TZID:GMT -0500 (Standard) / GMT -0400 (Daylight)
BEGIN:STANDARD
DTSTART:16010101T020000
TZOFFSETFROM:-0400
TZOFFSETTO:-0500
RRULE:FREQ=YEARLY;WKST=MO;INTERVAL=1;BYMONTH=11;BYDAY=1SU
END:STANDARD
BEGIN:DAYLIGHT
DTSTART:16010101T020000
TZOFFSETFROM:-0500
TZOFFSETTO:-0400
RRULE:FREQ=YEARLY;WKST=MO;INTERVAL=1;BYMONTH=3;BYDAY=2SU
END:DAYLIGHT
END:VTIMEZONE

Microsoft has chosen to treat the new US daylight savings time
transitions as if they begin in 1601, 147 years before Ben Franklin
first mentioned the idea of DST publicly, 406 years before the new
timezones actually go into effect.

Chandler maps timezones into Olson timezones based on the DST
transitions near the start of the event.  Since this event started in
2006, we didn't find an appropriate timezone.  I believe iCal may have
the same problem.  Beware if you'd like to interop with Outlook.

Sincerely,
Jeffrey