def self.all_by_date(year, month, day)
  year = year ? year.to_i : Tme.now.year
  month = month ? month.to_i : Time.now.month
  day = day ? day.to_i : Time.now.day
  date = Date.new(year, month, day)
  all(:conditions => {:created_on => date..date})
end