shahine.com/omar/

Unless you crawled under a rock, you should know that this year Daylight savings time has been extended by 4 weeks. This is a result of the Energy Policy Act of 2005. It will begin 3 weeks earlier in the spring, and end 1 week later in the fall. Cool you might think! Well not if you are a computer.

"The bill amends the Uniform Time Act of 1966 by changing the start and end dates of daylight saving time starting in 2007. Clocks will be set ahead one hour on the second Sunday of March instead of the current first Sunday of April. Clocks will be set back one hour on the first Sunday in November, rather than the last Sunday of October. This will make electronic clocks that had pre-programmed dates for adjusting to daylight saving time obsolete and will require updates to computer operating systems. The date for the end of daylight saving time has the effect of increasing evening light on Halloween (October 31)."

[Source: Wikipedia]

Microsoft has documented how different products will deal with this change. IMHO this is going to be a disaster as a number of products will not be updated and your appointments for 4 weeks of the year may be off by an hour.

If you recently launched Outlook 2007 on Vista, or after downloading the optional windows updates for XP you might be greeted with this dialog:

The bad news is if you own a Windows Mobile Device. Apparently it's up to the maker of said device to issue an update. What are the chances your carrier will release an update? I don't know; what is their track record for doing so up till now? Yeah, that's what I thought.

Seems like you can hack together a CAB file with the necessary registry changes to fix the problem. I'm a bit too lazy for that right now. Why we can't provide a download is beyond me.

Anyway this gist of it is this. All your appointments are created with a start time and an end time. Even All day events in Outlook (which is a design flaw IMHO, they should be floating events tied to a date, not an event that starts at 12am and ends at 12am in a given time zone). Well, the timezone information operates according to a timezone rule. The timezone rule is generally managed by the operating system. Well, when daylight savings time changes, the rule needs to be updated (the rule specifies the pattern for when daylight savings time starts and ends). Well, that's great... rule gets updated. But what about all the events that were already created that now live inside the window of the old rule and the new rule (for example, events that fall in the last week in march?) Well, all the events have to be updated to reflect the new start and end time. This has to be done manually by software. Ick. Here is what Microsoft has to say regarding Outlook:

Impact on Office Outlook calendar items

During the extra weeks of daylight saving time, calendar items in your programs will operate as if standard time is in effect unless you apply an update. Outlook, Microsoft Exchange Server, and other products use daylight saving time rules in effect since 1987.

Without an update, the following will occur for Outlook calendar items that are active during the weeks of March 11, 2007, to April 1, 2007, and October 28, 2007, to November 4, 2007:

• Single-instance appointments and reminders will appear one hour earlier than they should.
• Recurring appointments will appear one hour earlier than they should.
• All-day events will shift and span two days. Existing all-day events are associated with 24 specific hours instead of a given date. In the extra weeks of daylight saving time, the event appears to move backward by one hour, which is why all-day events will then span two days.

That's what the dialog above is doing. When Outlook is done you get a log file that has entries like so:

[Original Time Zone]
(GMT-08:00) Pacific Time (US && Canada)

[New Time Zone]
(GMT-08:00) Pacific Time (US && Canada) (Update)

[Time Zone Update Log]
Type: Appointment
ID: 040000008200e00074c5b7101a82e00800000000000000000000000000000000000000004d00000076436
16c2d55696401000000434430303030303038423935313144313832443830304330344642313632354439
3632314542443443343632333334354244424346414541433930393134374600
Subject: New Year's Eve
Old Start Time: Monday, December 31, 2007 8:00 AM
New Start Time: Monday, December 31, 2007 8:00 AM
Old End Time: Tuesday, January 01, 2008 8:00 AM
New End Time: Tuesday, January 01, 2008 8:00 AM
Recurring: No
Result: Success

...

Now I'm set with Outlook... but hosed on everything else.

Update: for a complete list of vendor fixes see this.