Daylight Savings Time Resources
Saturday, 24 February, 2007, 20:07 PST

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A number of governments around the world will be changing the beginning and ending dates for the timezone shift known as daylight savings time.  In the United States, DST will begin on the second Sunday in March at 0200, and end on the first Sunday in November at 0200.  If you reside in an affected country and timekeeping is important on your computer equipment, then you may need to manually intervene, depending upon your system.  Amateur radio operators in particular (who are frequently known for their thriftiness and resourcefulness) may be affected by this more than the general population of computer users, as hams are more likely to have some very old hardware and software still in operation.

Below are a few resources that might interest you if you are running Linux, Solaris, or an older version of Windows.

Windows
In the Windows world, if you are running Windows XP SP2 or Windows 2003 Server, these systems are supposed to be already set to go if you are keeping your Windows updates current.  I can confirm that I checked an XP workstation at the office with a timezone editor (that I will elaborate on below), and it was indicating the correct dates of change for DST.  Windows Vista is new enough that it is not supposed to require any attention at all.

All older Windows versions, including XP pre-SP2, will need some manual attention.  As far as manual configurations are concerned, I can't imagine anything much easier to use than the Microsoft Time Zone Editor, which has been included in Windows 95 Power Toys and various subsequent resource kits.  This tool should work in Windows 95, 98, ME, NT 4, 2000, and anything newer.  I have placed tzedit.zip on the server here.  It is a nice, tidy little download of 23kB, and requires no installation.  After extracting it, just run tzedit.exe from wherever you want.  The interface is fairly self-explanatory, but there is a Windows help file included if you need some clarification.

Linux
If you are a Linux user with a fairly recent version of your chosen distribution, you most likely have an update available directly from your distribution's web site.  If not, you can "roll your own." You'll need to obtain a new timezone source file, or edit an old one, compile it using zic, copy the compiled timezone file to /etc/localtime, and check it using date and/or zdump.

• Retrieve latest timezone source files from ftp://elsie.nci.nih.gov/pub/ . Download and extract the tzdata*.tar.gz file.  I placed a copy of tzdata2007b.tar.gz here, also.
• Compile the files you need, e.g. "northamerica" using zic.  O'Reilly has a page on zic that might help you with the syntax here, or check the manpages.  The compiled zonefiles are often kept in /usr/share/zoneinfo.
• Find the newly compiled zone file that you will be using, and copy it to /etc/localtime.
• Check to see if it updated properly using something like zdump -v /etc/localtime | grep 2007 and see if the dates and times of DST change are correct for your location.
• Run date to see if your system is happy.
• Troubleshooting is beyond the scope of this article, but I can state that I needed to use timeconfig on one of my Slackware 10.2 boxes after applying the update to settle everything down (however this was the only "problem child" out of 18 Slackware and Gentoo boxes that I administer).

Solaris
As of this date, Solaris users can find the information they need at sunsolve.sun.com/search/document.do?assetkey=1-26-102775-1

Cisco
Cisco IOS devices can be easily configured from the CLI.  A sample of how this would be done for my timezone (Pacific Daylight Time) on any IOS device would be:

 

Other
More information available at www.linux.com/howtos/TimePrecision-HOWTO/tz.shtml and www.dstpatch.com/ .

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