Often times in an application you might want to know how many of a given model were created today. Rather than writing a custom method for each model, let’s keep it DRY and extend ActiveRecord:

class ActiveRecord::Base
  def self.new_today
    if self.new.respond_to?(:created_at)
      self.count(:all, :conditions => "created_at > (NOW() - 60*60*24)")
    else
      nil
    end
  end
end

This will return the number of records created in the last 24 hours by calling the model with new_today (e.×. User.new_today). It will return nil if the model does not respond to the created_at Rails timestamp attribute.