2007 Daylight Saving Time Changes
Beginning in 2007, Daylight Saving Time (DST) has been extended by four weeks. It will begin on the 2nd Sunday of March (March 11th) and end on the first Sunday of November (November 4th). This change will have an impact on many computer operating systems and on calendaring software.
Unless certain updates are applied to your computer, it is possible that the time zone settings for your computer's system clock and calendaring software may be incorrect during the four additional weeks of Daylight Saving Time this year. This depends on where you live and which time zone you have selected.
When your time zone settings are incorrect, your clock may be off by one hour, and certain applications running on your computer may not display the correct time.
Microsoft and Apple have released patches for their more current operating systems that account for the new DST rules. In addition, most calendar software products have patches to correct for the new DST rules.
Older operating systems like Windows 2000 Professional and Windows XP Professional Service Pack 1 do not have patches that correct for the new DST rules. If you use one of these end of life operating systems, you will need to manually update your system clock (see instructions below).
To minimize the impact that the new DST rules will have on your day to day activities, it is important to apply DST-related patches in a specific sequence. Your Local Support Provider (LSP) can provide you with information about how patches are being or should be applied in your area. A general rule of thumb is that operating system patches should be applied first, followed by application-specific patches such as those for Microsoft Outlook.
Within your calendar:
When you or your LSP apply the updates:
Operating System Updates
Windows Vista is compliant with the new Daylight Saving Time and Standard Time rules.
Windows XP Service Pack 2
Download and install the DST patch from Microsoft. Note that this patch started pushing out as a High Priority fix via Automatic Update on February 14, 2007, so you may already have installed it.
Windows XP Service Pack 1 & Windows 2000 Professional
Manual adjustment of the system clock will be required to accurately reflect DST on March 11, 2007. At that time, you should also uncheck the box next to "Automatically adjust clock for daylight saving changes" in the time zone section of the Data and Time control panel. Manual adjustment of the system clock will again be required on November 4, 2007 to accurately reflect Standard Time.
Steps for manual adjustment of the system clock:
Please note that Windows XP Service Pack 1 and below and Windows 2000 Professional will no longer be supported at Penn beginning on July 1, 2007.
Mac OS 10.3.9 & Above
Run Software Update to install either the Daylight Saving Update (for Mac OS 10.3.9) or upgrade to (at least) Mac OS 10.4.6 which includes a fix for the changes to DST.
Meeting Maker 8.5.3
If you schedule meetings across areas that observe DST, Meeting Maker 8.5.3 will function normally, assuming that the system clock is adjusted for the new DST rules. If you schedule people and resources in different time zones across Arizona, Indiana, and International you will find that meetings will be off by one hour.
Outlook & Exchange
Microsoft has created a time zone update tool for Outlook. It is important that operating system level DST patches be applied before applying this patch.
Microsoft has also provided some recommendations to help minimize the effect of the extended DST period on calendaring.
For More Information
Microsoft's Preparing for Daylight Saving Time changes in 2007 is an excellent summary of the DST issues in Windows and Microsoft applications.
Apple has a general article about DST and various versions of the Mac OS.
ISC has a companion article to this one on Daylight Saving Time Changes For PDAs.
Information Systems and Computing
University of Pennsylvania
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