Convert local time to UTC in Rails
First I would check your time zone setting.
In your environment.rb (Rails 2) or application.rb (Rails 3) file, you can set the default timezone with: config.time_zone = 'Eastern Daylight Time (EDT)'
Secondly I would look at this post for information and guidance and tips to meet your needs:
http://databasically.com/2010/10/22/what-time-is-it-or-handling-timezones-in-rails/