I assume you're talking about the Event Scheduler.
In that sense, the Events are scheduled relative to the time on the site. So if you change your guild's time zone, that won't change the times the events are scheduled for, they'll say "10PM" regardless of the time zone your SITE is on.
The site you set your LOGIN to, however, will change the relative time of the events.
So if your site is in -10 GMT, and your login is set to -8 GMT, then the events will appear to be 2 hours later than they are actually scheduled on the calendar.
I seem to be having the same problem - everything was fine on our site until today when I get a phone call from a couple of my guildmates sayin that someone "hacked" the site because the times of all the raids changed and that it's showing a raid that was scheduled for 2 hours from now started already! Checked my login and the site time and both say GMT -7 so I can't figure out what happened.
Having a similar issue. The raids said they were starting 2 hrs before they should have.
I changed my personal timezone, then changed the "guild" timezone in the admin menu. This mucked up the starting time of all our raids, so I went through and fixed these all manually (cut & paste ftw). I think that is all fixed.
But now the site thinks it is Saturday already!! I can't seem to find an option to set the date anywhere. Is there one I am missing?