code: def on(self, year, month, day):
          
          return self.set(year=int(year), month=int(month), day=int(day))
docs: Returns a new instance with the current date set to a different date.
  
          :param year: The year
          :type year: int
  
          :param month: The month
          :type month: int
  
          :param day: The day
          :type day: int
  
          :rtype: DateTime