Time_zone_select

Rails
1

How does time_zone_select works?

I have:
<%= form.datetime_select :datetime, :default => Time.now %>

all datetime are in UTC in the database, here is two questions:

  1. how do I add the option for user to select time zone? how to user
    time_zone_select?
  2. what is the proper way to handle that in the controller? how to add
    the datetime and timezone?

deeply appreciate any help.