How Will Daylight Savings Time Rule Changes Affect Your Computer Systems?
In August of 2005, the US congress passed the Energy Policy Act. This changes the start and end dates for daylight savings time (DST). This law goes
into effect for the calendar year 2007. DST will start three weeks earlier, on March 11, 2007 and end one week later on November 4, 2007. As a result
the DST rules for all computer systems must change in order for the proper time zone to be applied based on these new rules.
This article will focus on the effect of various Windows Operating systems. There is significant impact on Office products such as Outlook that will
not be address in detail here. Please search Microsoft Support for KB931667 for details on dealing with Outlook and Exchange server issues.
Y2K all over again?
No, please don't panic! There has been some recent panic among computer support personnel that I have seen that is simply not needed.
In the worst case scenario, you can use the TZEDIT utility as described below and manually set the DST rules, even after March 10, and
you are fixed! The largest concern is on Windows 2000 and older systems that require manual intervention to apply the new rules. See below.
How will this affect my computer?
If your computer is set up to synchronize time with a server, time sync will update your time to the correct hour when DST rolls around, but your time zone
will not be correct unless you update each computer with the new time zone rules.
For example, Pacific Standard Time (PST) will not change to Pacific Daylight Time (PDT) on the correct day. For any stand alone machine, this is really
not much of a problem unless you have an application that is dependant on a correct time zone. For computers connected to corporate networks (domains)
and especially servers that are part of a cluster, this may be a big problem if not addressed. Read below on how to correct the time zone rules.
Windows Update possible problem
Windows update can have issues if your computer date, time and time zone are not correct. The issue is that the SSL certificate that
Microsoft uses for the Windows Update site may fail to authenticate if the date and time is too far off. Please be aware of this.
Fixing XP, Vista, Windows 2003 server
Updates to fix the time zone rules are being applied through Windows Update. Run all Windows updates by 3/10/2007 and your system will
be updated and ready to handle 2007 DST. You can use TZEDIT as described below to verify that the new rules have been applied to your system.
Also, as I understand it, if you are running Microsoft Outlook 2007, there is no manual intervention
needed. Search the Microsoft Support site for KB914387 for more detailed information.
Fixing Windows 2000 and older operating systems
There is no automatic update for these older systems. I don't know about you, but this one ticks me off! This is another ploy by Microsoft to push people
into upgrades. It would have been just as easy as they did for XP, to push out an update through Windows Updates that would correct the DST rules.
But no, they continue to make faithful users of Windows 2000 suffer with manual updates and further reduced support from Microsoft.
To apply the fix, search Microsoft Support for KB914387 and follow the instructions. There are reg files for changing multiple machines and
a utility called TZEDIT for a manual fix, one system at a time.
Download the utility from the KB914387 page and extract the files. Execute the TZEDIT.EXE. You will be shown a list of time zones with your current
time zone selected. Check the Start and End dates for DST in the bottom portion of the dialog window. If they are not starting in March and ending
in November, then they need to be corrected. To correct, with your current time zone selected, click the Edit button.
Make sure the "Automatically set Daylight Saving Time" check box is checked. Change the Start Day to Second Sunday of March at 2:00am.
Change the Last Day to First Sunday of November at 2:00am. Click OK, then click Close. This solution will only change the rules for your current time zone.
In order to change the rules for all affected time zones, the recommended solution is to apply the registry patch (.reg file) explained in KB914387.
In order for these rules to now actually take affect on your computer, you must refresh the TZI... see below.
Refresh the Time Zone Information
This is a required step! A system restart will not take the place of this procedure. There are two methods to take the new rules that have been applied
and load them into the running configuration, known as the Current Control Set.
Using either of the two methods above will force the rules from the Time Zone Information database to be loaded into your currently selected time zone.
- Method 1 - Open your Date and Time Properties window (double click on the time in you taskbar or open Date/Time on control panel. Now click the Time Zone tab,
then change your time zone to a different zone (any one will do), click Apply button, then change the time zone back to your current time zone again and click
Apply button, then click OK.
- Method 2 - Use the script that is provided in KB914387 called refreshTZinfo.vbs.
Keeping time in sync for XP and 2003 server
Open Date and Time Properties by double clicking on the time in your task bar (typically lower right corner of your desktop).
You will see at least two tabs named "Date & Time" and "Time Zone". There is a third tab named "Internet Time" that will appear if
your computer is NOT part of a domain with time synchronization. By clicking on the "Internet Time" tab you can check the "Automatically
synchronize with an Internet time server" and pick a time server in the Server drop down list. Now click the OK button and you are done.
Windows will not synchronize time with the time server when ever it is connected to the internet.
In the case that your computer is joined to a domain, but time synchronization to the domain is not set up, the "Internet Time" tab will
appear after 15 seconds or so. I believe that it takes that long for Windows to determine that time sync is not active.
Article Date: 2/22/2007