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2007 Daylight Savings Time Problem
Contents 1. Intro and General Information 2. Windows 3. Macs
4. Unix 5. PDAs 6. Applications 7. UICalendar

2007 Daylight Savings Time Changes for Apple Macintosh


In 2005, the United States congress passed the Energy Policy Act of 2005, which among other things extended the duration of Daylight Savings Time in United States, starting in 2007. Canada and Bermuda have followed suit.

The problem is that, during the extended periods of three weeks in the spring and one week in the fall, many clocks on systems which automatically to change to and from Daylight Savings Time will continue to operate on Standard Time, even though Daylight Time is actually in effect. These uncorrected systems will not be synchronized with other systems which have been fixed.

This page tells you how to correct that, so that the automatic Daylight Time changes take place on the correct date.

We have until March 11, 2007 to fix this problem in the U.S. and Canada.

Apple Mac OS X

Apple has released an Daylight Savings Time update for Panther as well as Tiger:

  • So you need to update to the most recent version of Panther, Mac OS X Panther 10.3.9,

  • Or the most recent version of Tiger, Mac OS X Tiger 10.4.8,

  • And install the Daylight Saving Time Update.

You should perform these upgrades prior to March 11, 2007.

This should be very easy to do: If you are using Panther or Tiger, to make sure that your clock maintains the proper time, simply install the updates that are shown for your computer in Software Update. You should install these updates even if your computer is used in a time zone that is not affected. If you want the standalone updates, see Apple Downloads. You need the downloads for Daylight Savings Time and for Java for Daylight Savings Time.

For more details about the available updates, see About Daylight Saving Time changes in 2007.

Previous Mac OSs

For more details about the available updates, or if you have an earlier Mac OS version, see About Daylight Saving Time changes in 2007.

  1. (Best) Upgrade to the latest version of 10.4 (Tiger) or 10.3 (Panther) : see About Daylight Saving Time changes in 2007.

  2. Change to and from Daylight Time manually by changing your Closest City.

  3. Operate your computer on UTC (Greenwich Mean Time) year round.

Even though it might be possible to download and install the Unix Zoneinfo files, like with other Unix systems, the Mac OS desktop uses a separate set of data files to control timezone adjustments for some desktop utilities, including the menu bar. Therefore, updating the Unix Zoneinfo files will not completely fix Mac OS X. The only complete fix is to upgrade to 10.3.9 or 10.4.5.

State of Indiana Information: As of Mac OS Version 10.3.9 or 10.4.5, the Mac's definition for Indianapolis now observes Eastern Daylight Time in the summer. The 10.3.9/10.4.5 update fixes both the Indiana problem, and the nationwide Daylight Time change date problem.
To Set Daylight Time Manually on older Mac OS Xs
  Note: You do not need to run this way if your operating system is Mac OS X 10.3.9 or 10.4.5 or newer.

In order to manually set Daylight Time on Mac OS X, you need to change what you have configured for your Closest City. For the summer, you need to find a new Closest City that is one time zone to your east, and also which does not observe Daylight Savings Time. Then for the winter, you should change back to where you really are, such as Chicago.

If you were to simply reset your computer's clock by moving the hands, then your computer's UTC setting would be wrong. If you select a Closest City that does observe Daylight Savings to switch to for the summer such as New York, then you'd spring forward a second time on the old change dates. If you disable automatic setting of the date and time, your computer will no longer sync its time with the Network Time servers, but instead it will drift inaccurately.

Perform these steps on the new "spring forward" date of March 11, 2007:

  1. Click (Apple) --> System Preferences --> System: Date & Time --> Time Zone (tab)
  2. Change your Closest City to one of the cities listed here. You need to find a city that is one time zone east of you, and also which does not observe Daylight Savings Time:
    • For Pacific Daylight Time (UTC-7) click on the Mountain Time Zone area on the map and select Phoenix - U.S.A.
    • For Mountain Daylight Time (UTC-6) click on the Central Time Zone area of the map and select Regina - Canada.
    • For Central Daylight Time (UTC-5) click on the Eastern Time Zone area of the map and select Quito - Ecuador.
    • For Eastern Daylight Time (UTC-4) click on central South America on the map and select La Paz - Bolivia.
  3. That's it for the spring. In the fall, on the new "fall back" date of November 4, 2007, reverse the above process and set your Closest City back to where you actually are, such as Chicago.
  4. Repeat annually.
When you make these changes to your closest city, note that your computer's clock is automatically set to the time in your newly selected time zone. You do not need to reset the clock yourself because you have kept automatic setting of date and time in effect.
To set any version of Mac OS X to UTC Year Round
  1. Click (Apple) --> System Preferences --> System: Date & Time --> Time Zone (tab)
  2. Click on the Western Africa portion of the map. Check to verify that the Time Zone shown is GMT.
  3. Select Monrovia - Liberia as your Closest City. (You cannot select London or any other European city, because they all observe Daylight Savings Time in the summer. The nation of Liberia does not; it remains on GMT/UTC year round.)
  4. Close the Date & Time window.

When you make this change, your computer's clock will automatically reset to the correct UTC time and date. Remember that in the evening in Chicago, it will be tomorrow in the UTC time zone.

Microsoft Entourage for Mac

Microsoft Knowledge Base Article 924606 "A calendar events that is dated on or after March 11, 2007 in Entourage 2004 for Mac displays the incorrect time for the event" This article contains a link to the patch. The patch is the Microsoft Office Version 11.2.5 upgrade; if your MS Office is already at a higher version, it has already been fixed.

See Also

The notes under 3. General Considerations on the introduction page. Various information there applies to Macs.

DST Problem Previous:  2. Windows Next:  4. Unix

2007-3-2  ACCC documentation
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