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February 27, 2007, Volume 53, No. 24

Making Sure You and Your Computer are
Ready for the March 11 Onset of Daylight Saving Time

Beginning this year, Daylight Saving Time (DST) will be in effect for four extra weeks, as mandated in the 2005 Energy Policy Act. DST will start on the second Sunday in March, three weeks earlier than previously, and end on the first Sunday in November, one week later than previously. This year’s actual start date is Sunday, March 11, 2007, at 2 a.m., and the end date is Sunday, November 4, 2007, at 2 a.m. Many newer electronic devices (computers, PDAs, cell phones, etc.) and recent versions of software will handle the change automatically; however, older devices and software programmed to gain or lose an hour according to the traditional DST schedule will need to be “patched” or have the time adjusted manually on the new DST dates. Check with your Local Support Provider (LSP) regarding recommendations and plans for patching the applications and systems in use within your department or office.

Key Products and the 2007 DST Change

Windows desktops and laptops: Systems running Windows XP Service Pack 2 will change to and from DST on the new dates automatically, provided the systems have been “patched” recently using Microsoft’s Update Service. Most University-owned Windows systems fall into this category. New Windows Vista systems will also change time automatically on the new dates. However, on systems running older versions of Windows, the time will need to be adjusted manually on the new DST dates. For instructions on adjusting your computer’s clock, please see the information at www.upenn.edu/computing/product/dst2007.html.

Mac OS desktops and laptops: Systems running Mac OS 10.4.6 and later will change to and from DST on the new dates automatically. Systems running OS 10.3.9 through 10.4.5 will also change to and from DST on the new dates automatically, provided they have been “patched” recently using Apple’s Software Update Service. However, users of earlier versions of Mac OS X will need to change their system time manually on the new DST dates. To change the time, go to the System Preferences for Date & Time, accessible from the Apple menu, reset the time and be sure to deselect the option to set date and time automatically.

Mobile devices: The system clocks of PDAs, smartphones, and other mobile devices also need to be adjusted for the new DST rules. Some vendors are providing operating system patches that users can install and others are requiring manual updates. Please see www.upenn.edu/computing/product/dsthandheld2007.html for details.

Calendaring Software: Users of calendaring software such as Meeting Maker and Microsoft Office Outlook/Exchange need to pay special attention to meetings scheduled between March 11 and April 1 and those scheduled between October 28 and November 4, when some participants’ calendars may be out of synch. Repeat meetings scheduled throughout the year may also be problematic. Users who synchronize their calendar between two or more devices may also see inconsistencies. To be safe, all repeat meetings/appointments as well as those scheduled for the date ranges above should be considered suspect until confirmed via email with all meeting participants. It’s also a good idea to print out, before March 11, your calendar for the subsequent four weeks to help check for possible problems.   

• The version of Meeting Maker calendar software currently used at Penn will work correctly for meetings that are proposed and accepted within the same time zone. However, meetings that are proposed or accepted across certain time zones (Arizona, Indiana, and international time zones), for example, by traveling faculty and staff, may show incorrectly, as may repeat meetings that occur during the DST period and beyond. To be safe, Meeting Maker users should heed the general advice in the previous paragraph.

• Microsoft Office Outlook 2007 handles the new DST dates correctly. However, Outlook 2003 needs to be patched. Please see www.upenn.edu/computing/product/dst2007.html for more information. To be safe, Outlook users should also heed the general calendaring advice above.

Kerberos: Anyone using Kerberized applications such as FTP or Kerberized email will be unable obtain a Kerberos tickets if their system time is incorrect.

Other software: Most desktop applications inherit date and time from the system and will handle time correctly provided the system time is correct.

Overall Recommendation

It’s important to update or patch your system in accordance with the information above and any local requirements, and to check meeting and appointment times because of calendaring issues. If you have questions or need assistance related to the time change, please contact your Local Support Provider. If you don’t know who your LSP is, please see www.upenn.edu/computing/view/support/. Regardless of the system and software you use, it’s wise to be on the alert for time-related problems for several weeks beginning on March 11 and again in the fall, beginning on October 28.

—Mark Aseltine, Executive Director, ISC Technology Support Services


Daylight Saving Time: New and Traditional Dates


2007 DST start date

Traditional start date

Traditional end date 2007 DST end date

2nd Sunday in March
(three weeks earlier)

1st Sunday in April

Last Sunday in October

1st Sunday in November
(one week later)

March 11, 2007, 2 a.m

April 1, 2007

October 28, 2007

November 4, 2007, 2 a.m.


Almanac - February 27, 2007, Volume 53, No. 24