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Is your Mac ready for Daylight Saving Time (DST)?

Daylight Saving Time comes 3 weeks early this year on March 11th 2007 (US). Europe DST comes into effect on Sunday, 25th March.

Simply updating the OS will not solve all of your DST problems. Software that calculates time internally using Coordinated Universal Time (UT, also known as Greenwich Mean Time or GMT). will also need to be upgraded. Many companies are not updating older software....and we thought there were problems with the time change in 2000.

Adjusting Date & Time for New Zealand Daylight Saving Time in late 2007. See Apple KB 306486 for fix.

The following updates need to be applied for the OS X Tiger and Entourage 2004.

  1. Office 11.3.3 (or newer)
  2. Apple Updates 10.4.5 and 10.4.6 (or newer)
    1. About the Mac OS X 10.4.5 Update: Updated the rules for time zones and Daylight Saving Time to conform to changes in the law for the United States, Australia, and other locations, for 2006 and later.
    2. About the Mac OS X 10.4.6 Update: Makes Mac OS X aware of United States Daylight Saving Time (DST) changes enacted by the Energy Policy Act of 2005.
    3. In addition to the Mac OS X updates listed above, the Java environment requires an additional update for compatibility with the time zone and DST changes described above.
      1. For Mac OS X 10.4 and Mac OS X Server 10.4, install Java for Mac OS X 10.4, Release 5. For more information about this update, see this article.
      2. For Mac OS X 10.3 and Mac OS X Server 10.3, install Java for Mac OS X 10.3, Update 5. For more information about this update, see this article.
    4. For WebObjects development and deployment environments, the WebObjects 5.3.3 update is also required. See this article for more information about the WebObjects 5.3.3 update
    5. See Important Points

Additional Links

Computing & Information Services, UNH

How This Change Will Affect Your Computer and What You Should Do About It for both Mac and PC

Rochester Institute of Technology articles (especially helpful for exchange environment.):

Daylight-saving time changes in 2007

Microsoft Time Zone Data Update Tool and daylight-saving time changes in 2007

MS Article: Preparing for daylight saving time changes in 2007

Mac Mojo blog: The Times They Are A Changin'

Amir's Exchange Clients Blog: DST 2007 Changes & Entourage 2004 for Mac


What if I'm using an older version of the OS and Office?

Daylight Saving Time Update (Panther) February 15, 2007 Apple released updates for Mac OS X 10.3 Panther.

Computing & Information Services, UNH Why you need to fix the Daylight Saving Time issue: steps to follow to download and install the CIS DST Fix package for Mac OS X 10.3.9 and below.

Daylight Saving Time Fix This is for all the OS X versions less than 10.3.9 that Apple did not provide a fix for to deal with the new daylight saving time issue. Posted on VersionTracker. Also see fix by CIS,NH above

Unofficial Daylight Saving Time Workaround for Entourage X posted February 27, 2007

Microsoft has indicated that Entourage X would not be updated for the new Daylight Saving Time rules. If you use Entourage with a Microsoft Exchange server, you should coordinate updates with your Exchange administrator, as Exchange must also be updated with the new rules.

Support for Office v. X (other than security updates) ended January 9, 2007, after 5 years. Support for 2001 ended long ago. Even though Apple did provide an update for Panther, Entourage X and 2001 will NOT be upgraded to support the change. (see Unofficial Daylight Saving Time Workaround for Entourage X )

A little history on how Entourage handled time changes. Previously, Entourage had it’s own way of calculating the time zone and matching-it up with various DST rules to reflect the event in your calendar. With the fix, time-zone calculation code was changed and Entourage now relies on the OS. Any application that does not adjust appropriately based upon system settings has a problem.

FWIW, my understanding is this time update was an extremely time consuming process..... not a simple fix as many think. See The Entourage User's WebLog More DST Changes


Other important points:

  1. Entourage clients updated with 11.3.3 Update will work fine BUT issues will come up when they interact with clients not updated with DST 2007 changes.
  2. Entourage 2004 11.3.3 supports DST changes by leveraging the OS. If you use this version (11.3.3 or newer) and a version of the OS that supports the DST changes (currently 10.4.6+), you are fine.
  3. If you use Entourage 11.3.3 with an older version of the OS (10.4.5-) that doesn’t support the DST rules, then the DST change will result in an inaccurate calendar.
  4. In simple terms: You MUST update both Entourage and the OS!


Options for users with older releases.

Change computers' clocks manually on 11-Mar-07, and then again on 01-Apr-07. Manually you will need to change clocks again on 28-Oct-07 and 04-Nov-07.
  1. If your computer uses a time server to set the date and time automatically, you can simply adjust the time zone (in the Time Zone pane of the Date & Time system preferences) to a zone that is an hour earlier or later, as appropriate.
  2. If your computer does not use a time server, you can simply adjust the time in the Date & Time pane of the Date & Time system preference.

Mac OS X versions 10.0.x through 10.2.8

If you're still using Mac OS X 10.2.8 or earlier, you can adjust your clock manually using Date & Time preferences. Deselect the option to set date and time automatically, then set the time for your local time zone as needed.

Mac OS 9.2 or earlier

Still using Mac OS 9.2? Use the Date and Time control panel to deselect the option to observe Daylight Saving Time changes automatically, then enable Daylight Saving Time manually. Applications that run in the Classic environment of Mac OS X will honor the Daylight Saving Time setting in Mac OS X.

Classic environment in Mac OS X

Applications that run in Classic will honor the Daylight Saving Time setting in Mac OS X.

Either way, there may be problems with software that calculates time internally using Coordinated Universal Time (UT, also known as Greenwich Mean Time or GMT).

See below for Geeky Fix


You can test to see if your time-zone file is already up to date by opening a terminal window and typing:

/usr/sbin/zdump -v /usr/share/zoneinfo/America/New_York | grep 2007

If you get a line back noting that April 1 (Not Mar 11) is the changeover date, then your Mac is not ready for the new DST standards.


Geeky Fix: Fixing the time-zone problem for 2007 on Macs with OSX versions below 10.4. http://research.dfci.harvard.edu shows how to test if your older system is up to date, and how to change the files appropriately.

Note the files referenced can be downloaded without entering user info and password.


Palm DST Update: Download this update from Palm.com.

Contributed by Diane Ross, Mac MVP