There has been a lot of discussion recently about the changes to daylight savings time in the USA. The changes have come about due to the 2005 Energy Policy Act. In previous years, DST in most of the USA ran from the first Sunday in April until the last Sunday in October. From 2007 DST will be from the second Sunday in March to the first Sunday in November. I’m based in the UK so these changes do not affect me directly but I work for a global company with a global Windows/Exchange environment so there is an impact to address.
Microsoft has had a patch available to address the issue since late November 2006. This has recently been updated to include DST changes in other time zones around the world. My recommendation is to deploy this patch to ALL Windows machines in your environment. The patch can be distributed via WSUS if you have this facility available.
Once the patch has been deployed you may need to correct entries in the Outlook calendar. Microsoft have provided two tools to do this. The first (http://support.microsoft.com/kb/931667/) is a tool that needs to be run individually for the affected users. The tool requires user interaction so you may want to distribute a link to a file share along with detailed instructions on how to run it and it’s potential impact. You should also give examples of why the tool is necessary so that the users have a good understanding.
The second tool is for Microsoft Exchange (http://support.microsoft.com/kb/930879) and will allow you to update the calendars centrally. If you are going to take this approach you need to carefully consider the risks of a blanket update. KB930879 lists the pros and cons of this method.
You can find more information from Microsoft about the DST changes here: http://support.microsoft.com/gp/cp_dst
There are now patches for Blackberry (http://www.blackberry.com/select/dst2007/index.shtml) and Windows Mobile (http://www.microsoft.com/windowsmobile/daylightsaving/default.mspx).