Currently Being ModeratedMay 24, 2013 8:24 AM (in response to curiousabout)
It sounds like there may be a setting toggled that we do not necessarily want. In Calendar > Preferences > Advanced, there is an option for "Turn on time zone support".
When this checkbox is selected, you can change the time zone for all events in the top-right corner of Calendar, and you can choose a different time zone for individual events.
The other symptom that might be occurring is if you are syncing this calendar with a service like iCloud, but you have a different time zone setup for that service. To change your time zone for iCloud, see the following article: