Daylight Saving Time changes: Mac OS X issues and fixes

Daylight Saving Time changes: Mac OS X issues and fixes

This coming Sunday, March 11th, new Daylight Saving Time changes will go into effect. Under the new scheme, Daylight Saving Time will be in effect from 2:00 AM local time on the second Sunday in March (March 11th in 2007) to 2:00 AM on the first Sunday in November. Previously, Daylight Saving Time was in effect from 2:00 AM on the last Sunday in March to 2:00 AM on the last Sunday in October. These changes affect the United States, much of Canada and some other countries.

This change obviously represents some issues for time-sensitive applications and Mac OS X itself. What follows is a summary of patches and workarounds being disbursed in hopes of obviating any potential negative effects from the time shift:

If you are running Mac OS X 10.4.5 or later, your system already has appropriate changes to deal with the new DST scheme. Still, you should still apply a patch released on February 15th (available in Mac OS X 10.4.8 and Mac OS X 10.3.9 versions) that enhances Mac OS X's ability to deal with international users that will also experience a DST change [note that there were a few troubleshooting issues associated with these patches, outlined in articles 1 and 2]. Unfortunately, these updates are only applicable to Mac OS X 10.4.8 and Mac OS X 10.3.9, not previous versions Tiger nor Panther. As such, if you are running Mac OS X 10.4.0 through Mac OS X 10.4.4 or Mac OS X 10.3.0 through Mac OS X 10.3.8, your system cannot be patched for the DST changes. You should consider updating to a newer release then applying the appropriate patch or using the freeware utility "Daylight Saving Time Fix" mentioned below.

In addition, if you are running Mac OS X 10.3.x or Mac OS X 10.4.x, make sure to apply the appropriate Java DST patch [Mac OS X 10.4.x | Mac OS X 10.3.x].

For systems running older versions of Mac OS X -- 10.0.0 through 10.2.8 -- there are two options:

  1. Manually set your clock forward one hour after 2:00 AM on Sunday, March 11th using the "Date & Time" pane of System Preferences. If you choose this route, you will also need to turn off the "Set date and time automatically" option -- also in the Date & Time pane, under the Date & Time tab.
  2. Use the freeware utility "Daylight Saving Time Fix", which will do the work for you.

According to Apple Knowledge Base document #305056, applications running in Classic will honor the time changes made under the host copy of Mac OS X.

Checking for compliance If you want to make absolutely sure that your Mac OS X system is set to comply with the DST changes, open the Terminal (located in /Applications/Utilities) and enter the following command:

  • zdump -v /etc/localtime | grep 2007

If the time is set to change correctly, the output should look like this (the example shown is for Pacific Standard Time):

  • /etc/localtime Sun Mar 11 09:59:59 2007 UTC = Sun Mar 11 01:59:59 2007 PST isdst=0
  • /etc/localtime Sun Mar 11 10:00:00 2007 UTC = Sun Mar 11 03:00:00 2007 PDT isdst=1
  • /etc/localtime Sun Nov 4 08:59:59 2007 UTC = Sun Nov 4 01:59:59 2007 PDT isdst=1
  • /etc/localtime Sun Nov 4 09:00:00 2007 UTC = Sun Nov 4 01:00:00 2007 PST isdst=0

Essentially, this command searches the localtime -- which harbors information about automatic DST changes to date and time -- file for entries that mention 2007, and presents the results. The output shown above indicates correct timing for the shifts: Sunday March 11th at 2 AM local time, and Sunday November 4th at 2 AM local time.

Individual applications, other consideratons Many time-sensitive applications have been updated by their developers to adhere to the changed Daylight Saving Time scheme. Some of the more prominent issues/patches include:

Office 2004 The appropriate DST changes were made in version 11.3.3 of this suite. Make sure you are using at least that version to comply with the new scheme. The current release, Office 2004 11.3.4, is available from VersionTracker.

Office v.X Although the Microsoft Mac BU updated Office 2004 for the DST changes with version 11.3.3, Office v.X was end-of-lifed on January 9th, meaning that it will not receive an official update through for the DST changes. However, an anonymous group has posted a workaround that will largely resolve any problems arising from the changes, as follows:

  1. Quit Entourage X
  2. Make a backup copy of your Identity. How to find your Identity.
  3. Make a backup copy of the existing timezones.ics file (located in /Applications/Microsoft Office X/Office/Timezones)
  4. Replace it with the new updated timezones.ics file.
  5. Launch Entourage X
  6. After installing this file, events in this time period (March 11 ? April 1) will still appear incorrect (unless you have previously manually offset the time so as to make them appear correct). You can force Entourage to re-calculate the correct time zone information by opening the event, making some small change (add a character to the title, then delete it again) and closing the event window so as to force Entourage to re-save the event. This script will do this for you automatically.

Synchronization apps/mobile devices (including iSync) Make sure to synchronize any mobile devices with your Mac after the DST shift takes effect. Many devices do not support automatic time-shifting, and as such will be one hour off until the next sync.


  • Mac OS X 10.4.8
  • Mac OS X 10.3.9
  • 1
  • 2
  • "Daylight Saving Time Fix"
  • Mac OS X 10.4.x
  • Mac OS X 10.3.x
  • #305056
  • Office 2004 11.3.4
  • workaround
  • new updated timezones.ics ...
  • script
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