vtam,
Actually, Exchange associates all events with a time zone, and there are several issues with Exchange implementations causing events to show off by an hour, or more. This can be because of time zones, or because of changes to daylight savings in a given region.
Microsoft even has a blog they list issue with time zones, and some of the steps it can take to get issues with them resolved.
For example this post mentions specifically if Time zone or Daylight Savings is off on the server (there is a minimum of about 1 cumulative patch (was about 4-5 patches before a cumulative was created), plus a data cleanup tool required to be run on each calendar on the server to apply all the changes to Exchange for the DST changes)
http://blogs.technet.com/dst2007/ (Microsoft Technet DST Blog)
These are the steps for an Exchange server admin to apply all the time zone updates, and then run the update tools:
http://support.microsoft.com/kb/941018
Hope this helps,
Nathan C.