Y2K mania all over again?  No stories of people stocking up their bomb shelters yet, but things could get a little interesting during the “extended DST periods” in March and November thanks to the Energy Policy Act    passed by the U.S. Congress in 2005.  The Act changes the traditional dates for daylight saving time (DST) in the United States, and most of Canada and the Caribbean islands are following suit.

When the law goes into effect this spring, DST will start three weeks earlier and end one week later than your software might expect.  IT Professional’s article Are You Prepared for Daylight Saving Time? recommends a risk assessment and remediation strategy. 

Hard lessons were learned when the Australian government changed DST to accommodate the 2006 Commonwealth Games. Microsoft added new time zones with the words "(Commonwealth Games)", causing problems with many software applications, including Microsoft Outlook .

Users of Vista can relax; it will handle the change automatically, and Outlook 2007 is covered too.  Microsoft is releasing a Windows patch  for earlier versions with updated time zone definitions and releasing an Outlook Time Zone Update tool.  Other applications might be affected too. Wondering if your software is compliant? Find out what Microsoft is doing to address the DST change. Office Online has a good article (derived from an upcoming KB) Prepare calendar items for daylight saving time changes in 2007.

Unix, GNU/Linux, and Mac OS X are Posix compliant, and use the zoneinfo utility that allows a single time zone to have multiple DST rules to handle changes like this one. SuSE Linux has already released their patch, and Apple included a patch in an OSX update.

Change in daylight saving time:

  • Previously DST started on: 4/1/07, First Sunday of April
  • With the new law, DST will start on: 3/11/07 Second Sunday of March
  • Previous DST ended on: 10/28/07 Last Sunday of October
  • With the new law, DST will end on: 11/4/07 First Sunday of November

Tips for avoiding scheduling problems:

  • Pay extra attention to appointments scheduled between 3/11/07 and 4/1/07, the "extended DST period." Make sure all attendees have correctly updated calendar items. Single meetings are more likely to be affected than recurring meetings.  Because they don’t contain time zone information, its impossible for the Outlook Time Zone Update tool to tell whether or not they need updating. 
  • Include time of meeting in the message body of your meeting requests.  If the time is not in the specified in body a meeting message, verify times with the organizer.
  • Put a reminder on your calendar for early March to print hard copies of your calendar during the extended DST period. Do this before you apply any patches with updated time zone definitions.
  • Once you have a printout of your calendar, run the Outlook Time Zone Update tool. Compare meeting times before and after updates and make sure everything is in sync.  
  • Update all of your connected devices need to be updated.  Don’t forget your phone and PDA.
  • Tell your friends! Running Outlook Time Zone Update only updates meetings you organized.  Every meeting organizer needs to run the tool to update meetings they’ve organized.  Have a delegate organizing meetings on your behalf? You need to update those too.  Find out more.  

If you rely on a raft of PDAs and other mobile devices, good luck.  But even if you loose a meeting or two, remember that things could always be worse.  Chaos was created in the 1950s and 60s when each U.S. locality could start and end DST as they desired. One year, 23 different pairs of DST start and end dates were used in Iowa alone. For five weeks each year, Boston, New York, and Philadelphia were not on the same time as Washington D.C., Cleveland, or Baltimore—but Chicago was. And, on one Ohio to West Virginia bus route, passengers had to change their watches seven times in 35 miles.  Imagine programming for that!