Setting up Timezone support in the past was a pain, but now with rails 2.1 and above it's easy and done in minutes. Here is what you need to do

# config/environment.rb
config.time_zone = "Pacific Time (US & Canada)"

# controllers/application.rb
before_filter :set_user_time_zone

def set_user_time_zone = current_user.time_zone if logged_in?

# Add to field to user model
add_column :users, :time_zone, :string

Once you have this in place then to user the users timezone in your app its just something like this

# To use users timezone rather then server time