Monday, March 5, 2007

Daylight Saving Time bug in Google Calendar

I have noticed what appears to be a bug in how Google Calendar handles the Daylight Saving Time transition.  Appointements after  March 11th are appearing an hour later than they do before.

For example, I have a weekly meeting shceduled for 3pm PST on Mondays.  On the 12th, the meeting appears to be scheduled for 4pm on March 12th.

There are a few reasons that this could happening:

  1. The meeting times are stored in local time, instead of UTC (I doubt that this is the problem.)

  2. The times are stored in UTC, but for display the calendar uses the time zone offset for the first occurance of the meeting

  3. The times are stored in UTC, but for display, the calendar uses the current time zone offset.

Hopefully it is the last one, as the meetings will correct themselves, once the Daylight Saving Time transition happens.  (Unfortunately, any new meetings created accross this transition will become incorrect.)

The "right" fix is to use the time zone offset for the day being displayed, before calculating the local time.  I have written support ticket #119726852 about this issue.

1 comment:

  1. Paul,
    The problem is in the VTIMEZONE definitions used by Google Calendar for recurring events. When you create a recurring event, it usually (but not always) gets created with the correct recurrence rule but the incorrect timezone definition (one that says DST starts the second Sunday in April).
    Google is aware of the problem, but hasn't said anythign about an ETA for a fix. See for a short discussion of the issue on the GCal GData API group.


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