Microsoft has set up a page to assist users with checking their Vista and XP system to make sure they are in compliance with all the local Daylight Saving Time (DST) rules. In some cases, time zone settings may be incorrect, according to Microsoft. There are no known issues with Mac OS X.
The Microsoft advisory says: "Observance of DST, and 'Summer Time' in much of Europe, is often different around the world; many areas, countries and territories shift their clocks at different times throughout the year. During these changes, clocks are usually shifted by one hour. Some locations follow a set of standard, uniform rules for the start and end dates of DST, but some locations determine the dates on a much more dynamic basis.
Microsoft, Windows Vista, Windows XP, DST, Daylight Saving Time