title: Rails 3 - Calculate time in users timezone
body: <p>I am creating a racing website for me and my friends.  When a user creates their account the choose their timezone from a select which I have populated with <code>ActiveSupport::TimeZone</code>.</p>
  
  <p>When the user creates a race they can select the time and timezone that the race is taking place.  Example:</p>
  
  <p>User has selected their timezone as Moscow which is -10 hours from UTC.  Another user then creates a race and selects the time 3pm in the afternoon in the timezone for Budapest, which is +3 hours from UTC.</p>
  
  <p>I have trying to figure out how to calculate what the race time would be in Budapests timezone, but I am struggling, am I missing a simply way to do this?</p>
  
  <p>Hope you know what I mean.</p>
  
  <p>Eef</p>