Thursday - March 01, 2007

Daylight Saving Time Headache

In August of 2005, the United States Congress passed the Energy Policy Act. The Energy Policy Act changes the start dates and the end dates of daylight saving time (DST). When this law goes into effect in 2007, DST will start three weeks earlier on March 11, 2007 and end one week later on November 4, 2007. These dates are referred to in this article as the “extended DST period.”

Now how does this affect you? In every way possible probably. You see, most of your electronic devices (including computers) that maintain internal clocks are programmed to switch to Daylight Saving Time from April to October. Some of these devices, like your cable TV box and cell phone, get their time “pushed” down to them from a central location and will not be affected. Other devices, like your personal computer have to be told about the new rules.

I’m going to offer you a little help to get you though this mess which will occur in 10 days. First of all, this will apply only to you folks in the United States and who are running (1) Microsoft Windows computers, which something like 98% of desktop users are running and (2) Linux, which I know a lot of you are switching to nowadays. I can’t help you with Macintosh computers because I rarely use them at work and am not that familiar with them. Contact Apple for information.

When you’re ready to start, click CONTINUE READING ...

Windows:

First of all, if you are running any of the following versions of Windows, your computer has probably already been updated via Microsoft Update (Windows Update on some systems). If you have automatic updates turned off, you need to manually run Windows Update to make sure your time zone data is updated. Microsoft is updating the following desktop versions:

Windows Vista (all versions)
Windows XP SP2 (all versions)

The following versions of Windows are no longer supported by Microsoft and you will need to follow the instructions here:

Windows 3.0
Windows 95
Windows 98
Windows ME
Windows NT
Windows 2000
Windows XP SP1

The first thing you need to do is download a little utility called TZEDIT. I have provided it here with help file and these instructions in TzEdit.zip. Click on that link and download the tool. It’s small, only 68K.

Once you unzip the TZEDIT package, you will have three files: TZEDIT.EXE, TZEDIT.HLP and EDIT.TXT. That last one being a text file with these instructions. If you’re ready to start, lets go. Go ahead and double-click on TZEDIT.EXE to start the program. Your screen will look something like this (your time zone may be different) ...

If you look at the bottom of the screen you will see that my computer is already set for the new Daylight Saving Time period - from the Second Sunday Of March to the First Sunday Of November. If your display says something different then click the Edit button and let’s start fixing things. The editor screen looks like this ...



Now, all you need to do is follow these instructions from Microsoft (which uses the Pacific Time Zone as an example - use your local time zone instead) ...

To manually modify time zone settings by using the Time Zone Editor, follow these steps:

1. Start Time Zone Editor.

2. In the Time Zones list, select a time zone, and then click Edit. For example, click (GMT-08:00) Pacific Time (US & Canada); Tijuana, and then click Edit.

3. In the Edit Time Zone dialog box, click to select the Automatically set Daylight Saving Time check box.

4. Specify the correct daylight saving time start date and end date. To do this, follow these steps:

a.  In the Start Day box, click the number of the day, the corresponding day of the week, and the month that you want. For example, click Second, click Sunday, and then click March.

b.  Select the time that you want to start daylight saving time. For example, select 2:00 A.M.

c.  In the Last Day box, click the number of the day, the corresponding day of the week, and the month that you want. For example, click First, click Sunday, and then click November.

d.  Select the time that you want to end daylight saving time. For example, select 2:00 A.M.

e.  In the Daylight Bias list, select how long you want the time to change when daylight saving time is in effect. For example, to set the clock forward 1 hour, leave the default setting of +1:00.

f.  Click OK.

g.  Select another time zone that has changed, and then repeat steps a-e. For more information about the time zones that have changed, click the following article number to view the article in the Microsoft Knowledge Base: 931836 (http://support.microsoft.com/kb/931836/) February 2007 cumulative time zone update rollup for Microsoft Windows operating systems

Repeat steps a through f for every time zone that has changed. When you have finished, click Close.

h.  Click Start, point to Settings, point to Control Panel, and then double-click Date/Time.

i.  Click the Time Zone tab.

j.  Select a different time zone than the (GMT-08:00) Pacific Time (US & Canada); Tijuana time zone, and then click Apply.

k.  Click (GMT-08:00) Pacific Time (US & Canada); Tijuana, and then click OK.

Note: Steps j and k are required for the new changes to take effect.

In this example, steps a through f update the time zone database. Steps h through k force Windows to read the time zone database and copy the updated information into the TimeZoneInformation registry key in the current control set.

That’s all there is to it. Don’t worry, you can’t seriously break anything if you screw up. You can always re-run TZEDIT to correct any mistake you made. Just be sure to follow ALL of the instructions above exactly like they are spelled out.

Linux:

Linux is actually a little easier but you have to start up a terminal screen because we can’t do this from any of the fancy desktops like KDE or GNOME. We are going to use the zic command-line utility. You can get more information about zic by typing “man zic” at a system prompt. Here are the instructions (which I got from Novell (who distribute SuSE) but apply to all flavors of Linux, including slackware) ...

1.  Download the most recent time zone data file (at the time of writing, tzdata2007b.tar.gz) from ftp://elsie.nci.nih.gov/pub/. Updates to this data file have the year and release letter updated.

2. Copy the file to a temporary workspace of your choice on the Linux system.

3. Extract the data with the following command:

tar xvfz tzdata2007b.tar.gz

4. Apply the updates for the region(s) of interest the system’s time zone data through the zic command. E.g., to update the North American data, run

zic northamerica

5. Relink the new time zone names with the old time zone names that were just updated with the following command:  (See the Additional Notes below for a workaround to possible error(s) in this step.)
zic backward

6. Verify that the updates are applied correctly with the following command

zdump -v timezoneofinterest | grep yearofinterest
e.g
zdump -v Canada/Mountain | grep 2007
The output from the previous step should look similar to this:
Canada/Mountain Sun Mar 11 08:59:59 2007 UTC = Sun Mar 11 01:59:59 2007 MST isdst=0 gmtoff=-25200
Canada/Mountain Sun Mar 11 09:00:00 2007 UTC = Sun Mar 11 02:00:00 2007 MST isdst=1 gmtoff=-21600
Canada/Mountain Sun Nov 4 07:59:59 2007 UTC = Sun Nov 4 01:59:59 2007 MST isdst=1 gmtoff=-21600
Canada/Mountain Sun Nov 4 08:00:00 2007 UTC = Sun Nov 4 02:00:00 2007 MST isdst=0 gmtoff=-25200

7. Relink the localtime setting (in /etc/localtime) with the corrected timezone information using the following command
zic -l timezonename
e.g.
zic -l Canada/Mountain

Note: If you encounter error(s) executing zic backward

Executing zic backward may return errors if other time zone data is not recent enough. One option would be to update those time zone as well in the same manner as noted in step 4 after identifying the specific time zones involved.

A workaround in this situation is to extract only the time zones from backward that need to be re-linked following execution of step 4 above. In this case that would be the time zones that are listed in the northamerica file. The following steps can be substitued for step 5 above:

grep ‘America’ backward > backward.america

zic backward.america

Most of the major distros of Linux (Red Hat, SuSE) have supplied patch packages to automate this process. Check with your vendor to see if they have one.

GET ME OUT OF HERE ...

Posted by The Skipper     on 03/01/2007 at 06:21 AM   
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• Comments (8) • Trackbacks(1)  Permalink •  

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