There are 2 places where the time zone can be edited and set on your account.

The ‘Default Time Zone’ for your whole account is the initial Time Zone that everyone in your account sees initially.  This is initially determined by your Administrator and it can be changed by the Account Admin from the ‘Administration’ tab, then ‘Account’ and ‘Edit Information’ (Figure 1 below).

This time zone will be used for all new users as a default unless you specifically change it when you build their login.

If you want to change the time zone for yourself alone when you login (the default might be EST, but you are on PST) then you can do this by selecting ‘My Profile’>’Edit My Preferences’ (Figure 2) and then your events and invitations etc. will be based around your personal time Zone.