To fix a problem with the timezones displayed in your email first check to make sure that you computers timezone setting is correct. In Windows double click the clock in the system tray near the bottom right of your screen. Then click the timezone tab and select your timezone.
If the timezone on your computer was correct go to your Google settings here :
https://www.google.com/accounts/EditUserInfo?service=mail
Check the box to
Display all Timezones and then select your timezone from the above list.
When you are done click the
Save button near the bottom left of the page.
Update:
Settings -> Accounts -> Other Google account settings -> Products -> Sign in to dashboard -> Edit personal information