Turn Off Time-Zone Sensing To Improve iPhone Battery Life?
To fix the alleged bug and avoid the battery drain, head to the Settings app in iOS 5 and tap Location Services and then scroll to "System Services" at the bottom of that window. Then switch off "Setting Time Zone".
It's not an official bug yet, though Apple is reportedly working on iOS 5's battery life issues. Anecdotal evidence suggests flipping this switch may significantly improve battery life.