Rails 3 stores all times in UTC format, and will often end up displaying times in the server’s timezone (depending on the settings). So, unless your server is in the same timezone as ALL your users, they may well end up very confused.
I needed to address this on a recent project. Here’s how I set the timezone on every request, so users see the proper time:
Yup, just a single commit.
It adds a jQuery cookie management library. A small js file then sets the browser timezone in a cookie, which is sent to the app on every request. A simple before_filter in application_controller.rb kicks Rails into the proper time zone for the duration of the request.