Washington Apple Pi

A Community of Apple iPad, iPhone and Mac Users

Daylight Saving Time - Is Your Computer Ready?

© 2007 Pat Fauquet

Washington Apple Pi Journal, reprint information

Each spring and fall people around the world reset their clocks to make more effective use of natural sunlight in summer time. Although Ben Franklin mentioned the idea as early as 1784, the United States did not adopt Daylight Saving time until 1918.

For many years the time to reset clocks in the United State was set as 2:00 a.m. on the first Sunday in April and the last Sunday in October. However, when the US Energy Policy Act of 2005 was passed in Congress, a little known adjustment was made to these dates. Beginning in 2007, daylight saving time will change on the second Sunday in March and the first Sunday in November.

At first glance, this change seems inconsequential, but in fact, this change is guaranteed to wreak havoc in the world of technology. Software patches will need to be applied to many operating systems and applications. However, most of us are not yet aware of the change and few are aware that any device that automatically changes its clock to match Daylight Saving Time needs to be updated with a software patch to work correctly.

Apple Inc. included the fix starting with Mac OS X Tiger 10.4.6, so Macintosh users who keep their computers up-to-date are ready for the change. However, users of earlier operating systems may have some real problems.

Email messages will have the wrong timestamp and calendar events will not be reset to reflect the correct time. Larger problems loom for people who use network-based services such as email servers and file servers. The difference of an hour can cause recent changes in documents not to be recognized, and therefore not saved correctly.

Users of Mac OS 10.3 and 10.2 will not be able to rely on Apple Inc. for a fix since they are no longer updating those operating systems. However, Ian Ward Comfort of Stanford University has released a patch to solve the problem. It can be found at http://www.afp548.com/. The fix can be downloaded as a disk image or as a script.

If you are not using Mac OS 10.4 or if you do not want to use the patch, you will need to manually change the time on your computer's clock for three weeks in March and one week in November each year.

There are two options for re-setting your clock:

• If you are using the Date & Time System Preference in Mac OS X, adjust the time zone to a zone that is one hour earlier or later, as is appropriate. You will need to re-adjust your time zone on the first Sunday in April and the last Sunday in October. Another solution would be to turn off network time for the weeks around the change, then turn in back on for the rest of the year.

• If you do not use a time server, adjust your clock manually.

Some calendaring software such as Microsoft Entourage will also need to be updated. The Microsoft Office for Mac 11.3.3 update fixes the problem for the latest version of Office, but it does not fix earlier versions of the software.

If you are also a Windows user, be sure to check Microsoft for patches and fixes for their software. 

You may also want to check for updates to your Palm PDAs and Blackberrys. Don't forget about more advanced VCRs that also automatically adjust for Daylight Saving Time.

Each year as you reset clocks around your home, don't forget about digital cameras and other devices that date and time stamp their files.  Keeping every device set to the correct time helps prevent data loss.