As we all know it, Time Zones are a pain in the neck. Rails make things easier by providing some nice helpers. However, I recently faced a challenge when trying to pre select a time zone for a user. Using the time_zone_select helper, there's simply no way you can pre select a timezone for a user unless you already saved the time zone in his/her record. Creating a new user or editing a user with an optional timezone, becomes quite a challenge.
That's why I created this patch:
http://dev.rubyonrails.org/ticket/10590
The patch adds support for a :default option allowing to select a default time zone if the user's time zone isn't set already.
I also added updated the help with usage examples.