• What daylight saving time changes?
• How does this affect my computer?
• How do I fix my Windows computer
• How do I fix my Apple computer
• I use Microsoft Outlook. How will this affect me?
• I use another calendaring system. How will this affect me?
• How does this affect Java?

As you may be aware, the government changed the start and end dates of Daylight Saving Time (DST) this year. Instead of starting on the first Sunday in April, it starts this year on the second Sunday in March (3/11/2007), and will revert back to standard time on the first Sunday in November (11/4/2007) instead of the last Sunday in October (10/28/2007). This has caused a serious problem for some computing devices, many of which are programed to automatically adjust the time for DST. An even larger concern is the impact this change will have on some calendaring programs, which may cause appointments to be listed incorrectly.

Most computers automatically change their clocks to adjust to DST. Without being updated to reflect the new rules, your computer will not change the clock until April 1st, so for three weeks in March, it won't be correct.

Late last year, Microsoft released a critical update for Windows XP that addressed the time change issue. We pushed this update out to our domain computers at that time, and we would expect that most people who have automatic updates on their own computers would have also applied the update. They've since released an update that address changes in some foreign countries, and we pushed it out earlier this month.

Microsoft is no longer supporting Windows 2000 with updates other than security updates, and older versions, like Windows 98 and ME are not supported by Microsoft at all. We do have a program that will update the time zones on Windows 2000, 98 and ME. We can't deploy it remotely, so please e-mail support if you have a computer running one of those versions and would like it patched.

If anyone is already running Windows Vista, it shipped with the new DST data, and doesn't need patched.

More information is available from Microsoft in this Knowledge Base article

Versions of OS X starting with 10.4.5 already have the correct rules. Apple released an update on January 8th to update OS X 10.3 and 10.4, which is avaiable through Software Update. Older versions of Mac OS are not being updated. Apple suggests deselecting the option to automatically adjust for DST, and to change the clock manually.

Apple has more details about the updates in this article.

If you use Outlook's calendaring features, any appointments you made before your computer was patched that fall between March 11th and April 1st (when the switch to DST would have occured under the old rules) will be off by one hour. The same will happen between October 28th and November 4th. Microsoft has released a tool that will shift all of your appointments by an hour, but would also shift any apointments you set after the timezone shift by an hour, so the apointments put in after the patch would be incorrect. Had we been aware of this when we pushed out the timezone patch, it wouldn't have been such an issue, but unfortunately Microsoft didn't add this cavet about Outlook's behavior until about 6 weeks after releasing the patch. Here's an example of the specific behavior you can expect to see:

You scheduled an apointment for 8:00 AM on March 20th before the patch was applied to Windows (late November or early December). Now that the patch was applied, it will appear on your calendar at 9:00 AM on March 20th, and you'll be an hour late to your appointment.

If we run the tool on your computer that would fix the appointments, we'd hit another problem:

You scheduled an appointment for 8:00 AM on March 20th after the patch was applied to Windows. It would be correct, but if we run the tool to fix the older appointments, this one will be affected too, and the appointment will show up on your calendar at 7:00 AM on March 20th, and you'll be an hour early to your appointment.

Unfortunately, we don't have any way to fix this problem. If you need more help understanding the problem, we'd be happy to try and work with you, but really you'll have to try and decide what time your appointments were supposed to be. Microsoft is recommending that people contact the other people they're meeting with the confirm appointment times during that three week period. Additionally, they suggest adding the time as part of the text of the meeting (i.e. - "Meeting with Bob at 8AM") for appointments during that period.

Here's a list small list of calendar software and PDAs. The computer or PDA the calendar is running on would still need to be updated to have the correct time, but this list will help you determine if there are any extra issues you need to be aware of.

Not affected:

• iCal
• Calcium
• Google Calendar
• Many Palm Devices
• Palm Desktop

• Microsoft Outlook
• Microsoft Entourage
• Palm Treo 700w & 700wx
• Windows Mobile Devices
• BlackBerry Devices
• Evolution
• iPod

Java does its own time calculation, independent of the computer's operating system. This means that Java also needs to be updated to reflect the new rules. Versions of the Java Runtime Environment starting with JRE 5 Update 6 have the correct rules for the US. We push the Java Runtime Environment out to our domain joined PCs, so we'd expect most to have the correct rules.

Sun has an article with much more detail about the problem.