def end_of_month
      last_day = ::Time.days_in_month(month, year)
      last_hour(days_since(last_day - day))
    end
def end_of_month
      last_day = ::Time.days_in_month(month, year)
      last_hour(days_since(last_day - day))
    end
Returns a new date/time representing the end of the month.
 DateTime objects will have a time set to 23:59:59.