DST changes: What you need to know

What has changed?

Daylight Saving Time (DST) was extended by four weeks, starting in 2007, by the Energy Policy Act of 2005.  Under the new schedule:

  • Clocks "spring forward" by one hour on the second Sunday of March rather than the first Sunday of April. 
  • Standard time returns, and clocks "fall back" by one hour, on the first Sunday of November rather than the last Sunday of October.

The first "extended DST period" for 2007 was between March 11 and April 1 -- and the tail end of the extension is between October 28 and November 4 this fall.  That's the period of concern.

What do I need to worry about? 

Most computer operating systems and applications software for mainframes, server computers, desktops, laptops, and handheld devices like smart phones has by now been "patched" (upgraded) to take account of the new DST schedule. 

System administrators took care of patching mainframes and servers.  In many cases your desktop, laptop or handheld was automatically patched.  However, depending on your circumstances, you might have been (or still may be) required to take some actions on your own.  That is explained in the questions below.

Due to the complexities of the software changes, it cannot be guaranteed that ALL transactions that rely on computer calendars will shift correctly.  You should consider the time of all computer time entries in the extended DST period  particularly those in computer-based calendars, as suspect until confirmed.

What's the best way to confirm I have the correct times?

We recommend that you "confirm" the scheduled time for appointments in the extended DST period by typing it in the subject line of those events. Where that is not possible, a confirmatory telephone call prior to an appointment may be a very good idea.

What will I (did I) notice?

You have seen notices for system administrators about software patches -- or automated notifications from the software itself, if permission from you was required to install the patches or you needed to re-boot your computing device to make them effective.

You may notice some calendar items in the extended DST period are "off" despite successful patching.  When calendars are set to synchronize (e.g., between a handheld/phone and a desktop, by way of a server) a mistaken change in any one may propagate to all the others.

Why is this so complex?

It's the interaction of multiple software upgrades applied at different times -- to your computer's operating system (OS), its email/calendar software, and the OS and email/calendar software of server computers with which your computer interacts -- that makes the process uncertain. 

Unfortunately, today's computer software was not designed for shifts in the DST schedule, nor to differentiate between an event update aligning to such a shift and an actual change of an event's time.

How will (did) Windows computers cope?

Most computers running Windows XP were automatically patched to adjust the system clock according to the new DST schedule.  Windows systems that don't take advantage of automatic updating, or are running a legacy Windows OS (Me, 98, 95 and, in some cases, 2000), require a manual patch.  

Managed Windows XP and 2000 systems on the medical campus -- that is, those that are part of the "Medical" domain -- received DST patches automatically from Medical Information Technology back in March. 

Windows XP and 2000 systems that are operated off campus, outside the Medical domain, must rely on Windows Update services for the DST patch.  No updates are available for older Windows OS (95, 98, Me).

For details, see the Windows entries DST change information by system.

How will (did) Mac computers cope?

As with Windows systems, most computers running Mac OS X were automatically patched for the new DST schedule.  Mac systems that don't take advantage of automatic updating, or are running a legacy Mac OS, require a manual patch. 

Medical Information Technology cannot use centralized patching tools for Apple/Mac systems.  You must have automatic updating turned on, or perform the update by manual request.

For details, see the Mac OS entrites in DST change information by system.

Will (did) portable devices like smart cell phones and other handhelds get patched too?

Most communication devices running Blackberry, Palm or Windows Mobile operating systems would have received patches from servers, provided the system administrators pushed them out. 

Medical Information Technology pushed out patches for medical campus Blackberry devices and those (such as Treos) receiving Goodlink services in March.

As noted above, if your handheld device synchronizes with another calendar (over the cell phone network or via 802.11 wireless) patching on the server may cause unwanted changes there to migrate to the calendar on your handheld (and vice-versa).   The same warnings about "confirming" appointments apply.

For details, see the entries related to mobile devices in DST change information by system.

What about mainframe and servers?

Mainframe and server software should long ago have been patched to reflect the new DST schedule, or have in place procedures to change systems clocks manually.  Still, you should check the system clock on systems you use, particularly on 28 October.

More information

Daylight Saving Time Help and Support Center (Microsoft)
The place to begin if you have a system running Windows

About Daylight Saving Time changes in 2007 (Apple)
And the place to begin if you have a Mac.

Daylight saving time (NASA)
Brief overview of DST and the schedule for the next 5 years

Daylight saving time (NIST)
More about DST and links to all kinds of information about time

Daylight saving time (WebExhibits.org)
More still about  DST