Beginning March 2007, daylight time is in effect a total of four weeks longer than previously.
Computers running Windows XP or older operating systems need to be updated so your computer time is correct.
If the time zone being updated is the time zone the system is on, it calls the API function Set Time Zone Information() to update the information that the kernel reads at startup in the registry.
After this, it updates a structure in the system that contains this information as well as send out a WM_SYSTEMSETTINGSCHANGE message to running applications The first problem described above seems to be happing during step #3.
Out of the box, XP and the new DST changes don’t get along. For a single machine, I found the most straight-forward way to update your machine is through TZEdit.It should have changed automatically for DST since I had the box checked, but it didn't, so I thought it odd I had to change it manually for DST.But it won't stay changed, it keeps jumping back an hour after about an hour's time. In the Internet Time Settings window, make sure that the box for Synchronize with an Internet time server is checked.You can now select one of the provided time servers from the drop-down list, which includes Microsoft’s own time server (time.windows.com) as well as several regional servers for the National Institute of Standards and Technology, popularly known as “the folks with the atomic clock.” But you’re not limited to the servers in the list; you can add any valid time server yourself by typing the address into the Server field.(Vista and Windows 2008 contain the 2007 changes to the US DST but the latest update should be installed so worldwide zones are current.) Use the Time Zone update tool for Outlook to fix your appointments.This tool was first introduced in Outlook 2007 RTM then released as a standalone tool for all versions of Outlook. (This tool is also good for changing appointments if you move to a new time zone.) There is a similar tool administrator can run on Exchange server. If you have a Dynamic DST key under any of the US or Canadian zones (as well as for a couple of other countries), it was installed.At the bottom of the time and date window, select Change date and time settings.In the Date and Time settings window, click the Internet Time tab and then select Change Settings.But sometimes a user’s Windows clock can go awry and display the incorrect date or time, usually due to hardware issues, a temporary loss of Internet connectivity, or online synchronization problems.If your Windows clock is wrong, but you’re currently able to connect to the Internet, you can easily set the correct time by re-synchronizing your PC with an online time server. Head to your Windows desktop and locate the clock on the far right side of the Taskbar (note that your clock may appear slightly different from the screenshots depending on your specific version of Windows and your Taskbar configuration settings).