Find last updated date for ActiveRecord model

Often a page needs to show when content was last updated, its easy to do when showing a particular record, but what about the last updated date for a list of records?

This is a little snippet I use:

date_of_last_fee_change = Fee.last_updated

To make it happen for all models:

ActiveRecord::Base.class_eval do
  def self.last_updated
    last = first(:order => 'updated_at DESC')
    last.try(:updated_at) 
  end 
end