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The rules for Daylight Savings Time in the United States change in 2007. Most people need do nothing, but it's important to know if you're most people.

I was forwarded some email that said the dates for Daylight Saving Time are changing, and that I need to take steps to make sure that my computer's clock would be set correctly. The links went to the Microsoft web site, but I couldn't figure out what I need to do, if anything.

What do I need to do?

Daylight Saving Time (DST) in the United States will be extended by four weeks, beginning this year. It'll start three weeks earlier and end one week later than it would have by the old rules.

So the question boils down to: how will your computer find out about the new rules?

As is so often the case ... it depends.

The good news is that for many of you, nothing is required.

Microsoft Windows

If you're already running Windows Vista, you're done. Vista already incorporates the necessary change. Nothing to see here.

If you're running Windows XP SP2, and you have Automatic Updates turned on (as I feel you should), you're done. Your copy of Windows either has been, or will be, updated in time for the new DST rules.

If you're running SP2 but don't have Automatic Updates enabled, then visit Windows Update sometime before March 11, 2007 to manually pick up the DST update.

If you're running Windows XP without SP2, you need to first install SP2 (as I feel you should), by visiting Windows Update. After the SP2 install, continue with subsequent updates, and you'll get the DST update as part of the bargain.

If you're running versions of Windows older than XP with SP2 ... Microsoft appears to provide no help. Personally, I'd visit Windows Update anyway, particularly if you're running Windows 2000. Support for Windows 9x is certainly over, but Windows 2000 still has a large corporate installed base, and it wouldn't surprise me if a fix were made available.

"If you're running Windows XP SP2, and you have Automatic Updates turned on (as I feel you should), you're done."

For those older versions, or if you elect not to take the available update(s), you'll need to do things manually, twice a year. You should first turn off "Automatically adjust clock for daylight saving changes" and then update your clock by hand on the second Sunday in March and on the first Sunday in November.

Microsoft Office

Microsoft Office is also affected by this change. (You should first update Windows.)

If you're running Office 2007, you're done. Office 2007 is already up to date with respect to this change.

If you're running older versions of Office, and if you use the calendar or reminders features of Microsoft Outlook, Microsoft has provided a Time Zone Data Update Tool for Microsoft Office Outlook.

Other Software

Most operating systems are affected one way or another, so if you're not running Windows, you'll want to check with your OS vendor. For example Apple's Mac OS X included updates for this issue in their 10.4.5 update. Other OS's that include an automatic update feature will typically also have handled this already.

Applications are more difficult to predict. Most will rely on the operating system to handle everything and will not be affected. Others, like Microsoft Office Outlook which have special calendaring and related features may be impacted and may need to be updated. Check with the specific application vendor if you're not sure.

Regardless:

Keep an eye out.

I would pay particular attention to your computer's clock on the following dates:

  • March 11, 2007 - the new start of DST. Your clock should "spring forward" one hour on this day. If you've applied the appropriate patches and have automatic adjustment enabled, it should do so automatically.

  • April 1, 2007 - the old start of DST. Your clock should not change on this day. If you failed to update, it might.

  • October 28, 2007 - the old end of DST. Your clock should not change on this day.

  • November 4, 2007 - the new end of DST. Your clock should "fall back" one our on this day.

And naturally, keep an eye on your other programs, particularly calendaring and scheduling applications to make sure that they're all following the new rules as well.

Article C2926 - February 7, 2007 « »

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Leo Leo A. Notenboom has been playing with computers since he was required to take a programming class in 1976. An 18 year career as a programmer at Microsoft soon followed. After "retiring" in 2001, Leo started Ask Leo! in 2003 as a place for answers to common computer and technical questions. More about Leo.

Not what you needed?

8 Comments
Bruce Watson
February 10, 2007 6:11 AM

I found this link to a Microsoft utility to allow manully updates to DST settings.
http://download.microsoft.com/download/5/8/a/58a208b7-7dc7-4bc7-8357-28e29cdac52f/tzedit.exe

Running this program opens a utility that allows you to set the start and end dates for your time zone.

This entire issue is discussed in depth at:
http://support.microsoft.com/gp/dst_topissues#a5

Carl
February 11, 2007 12:30 AM

I plan to run one or both of two venerable programs on my legacy Windows systems to reset their system clocks for daylight saving time. The programs are D4 and About time. These programs also set the DST flag. I also intend to turn off the automatic update DST flag on these systems as well.

It would behoove anyone using Outlook, Exchange and/or Exchange Server and several calandering applications to visit the Microsoft DST help and support site--a link immediately follows Leo's article.

Carl

Carl
February 11, 2007 12:35 AM

I plan to run one or both of two venerable programs on my legacy Windows systems to reset their system clocks for daylight saving time. The programs are D4 and About time. These programs also set the DST flag. I also intend to turn off the automatic update DST flag on these systems as well.

It would behoove anyone using Outlook, Exchange and/or Exchange Server and several calandering applications to visit the Microsoft DST help and support site--a link immediately follows Leo's article.

Carl

Duane Lambe
February 12, 2007 6:58 AM

Here's the stuff for Windows 2000; if you like to know what's happening behind the scenes, they have all the registry entries and VBS you'll need to "manually automate" the update. Also works on XP (confirmed).

http://support.microsoft.com/kb/914387

Tony
February 24, 2007 5:04 AM

Leo
You might want to recommend that users check MICROSOFT UPDATE rather than WINDOWS UPDATE so that they can receive all of the Microsoft patches for all of their software. Usually, folks forget about the other Microsoft products on their machines (such as WORD or OFFICE) and miss critical patches for that software.

Frank
March 9, 2007 6:57 PM

What changes would I have to make since I live in Arizona where we don't observe DST?

steve
March 12, 2007 8:26 AM

I have XP/SP2, with all current updates. I even manually applied the DST patch from Microsoft (it said I didn't need it). But my system is STILL running one hour behind today.

Not everyone who simply trusts MS is "done"...

Patrick Tillery
March 14, 2008 9:28 AM

Apparently my Vista x64 attempted to change to DST time zone but didn't work. I keep getting a pop-up that says "You seem to have outdated time zone information. Please run Windows Update." Windows update did nothing for me. The Time Zone button in the "Date and Time" dialog box doesn't work. I have tried turning off UAC and Defender. HELP!

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