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Starting this year, the transition to Daylight Savings Time (DST) will occur on the second Sunday in March (March 11, 2007).  This is three weeks earlier than in previous years. The change is part of the U.S Energy Policy Act of 2005.  DST will also end one week later in the Fall on Nov. 4.

These changes affect most of the United States and Canada (but not Arizona, Hawaii, Peuerto Rico. the U.S. Virgin Islands and American Samoa).  They also do not apply to Mexico.

Most computers and other equipment that automatically keep track of local time will need to be updated to properly track this change.  Alternatively people can manually adjust the time on these systems.  You may also need to take this change into account  when making date/time calculations across time zones using local times as it is possible that one time zone but not the other is affected by the new law.

Microsoft Windows

  • Vista - already prepared to handle the DST change.  No need to do anything
  • Windows XP with Service Pack 2 - needs a patch which will be automatically installed if you are regularly doing critical updates.  If you are not then run Windows Update before March 11.
  • Older versions (XP with SP1, Windows 2000, NT, 98/95) - not supported and there is no simple automatic fix.  We recommend that you disable the automatic DST adjustment and set the time manually.  To turn off the automatic DST adjustment, open the Windows Control Panel and select Date/Time.  If there is a Time Zone tab select it.  Remove the check mark from the option to "Automatically adjust clock for daylight savings changes."

    Alternatively there is a Microsoft supplied  program, called tzedit.exe, that you can get for some older versions of Windows and run to make the adjuestments. Some people have reported problems with this utility, however, so we do not recommend it at this time.  Note: it is important to turn off automatic DST adjustment to keep your computer from making an additional adjusment on April 1.
For additional details see:

Apple Mac OS

  • OS X 10.4.5 and higher - already prepared although there is an additional update to adjust for recent changes in time zone rules around the world.  This can be installed on your computer by applying the DST Update found in Software Update.
  • OS X 10.3 - upgrade to 10.3.9 Panther and install the DST Update
  • Earlier versions - Deselect the option to set date and time automatically, then set the time for your  local time zone.  Note: it is important to turn off automatic DST adjustment to keep your computer from making an additional adjusment on April 1.
For addtional details see


  • Please see〈=en
  • Enter the command  zdump -v /etc/localtime |grep 2007 , you are OK if you see a result similar to

    /etc/localtime  Sun Mar 11 06:59:59 2007 UTC = Sun Mar 11 01:59:59 2007 EST isdst=0 gmtoff=-18000
    /etc/localtime  Sun Mar 11 07:00:00 2007 UTC = Sun Mar 11 03:00:00 2007 EDT isdst=1 gmtoff=-14400
    /etc/localtime  Sun Nov  4 05:59:59 2007 UTC = Sun Nov  4 01:59:59 2007 EDT isdst=1 gmtoff=-14400
    /etc/localtime  Sun Nov  4 06:00:00 2007 UTC = Sun Nov  4 01:00:00 2007 EST isdst=0 gmtoff=-18000

  • Unbuntu - recent distributions are OK, older may need an update of the libc6 package and the tzdata  file
  • Red Hat - see for what to do for various versions.

Java Applications

Java does NOT take timezone information from the operating system that an application is running on.  If you have time sensitive Java applications then it may be necessary to update the version of JRE (Java Runtime Environment) or JVM (Java Virtual Machine) that is being used. 

For additional details and updates see

Other devices

General advice

  • Check the time on all our devices as soon as possible after March 11
  • Check for possible time errors on your electronic calendars.
  • Be alert for possible time scheduling inconsistencies until April 1.
  • Double check the time after April 1 to make sure that your devices did not make an aditional time change.
  • When scheduling meetings, especially with people outside the US and Canada, make sure that everyone is aware of the earlier shift to DST. 


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Last updated March 9, 2007
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