   @type time_zone_database :: module()
 
   @doc """
-  Returns how many days there are in the given year-month.
+  Returns how many days there are in the given month of the given year.
   """
   @callback days_in_month(year, month) :: day
 


  @doc """
  Parses the string representation for a datetime returned by
  `c:datetime_to_string/11` into a datetime-tuple.

  The returned datetime must be in UTC. The original `utc_offset`
  it was written in must be returned in the result.

  Specifies the time zone database for calendar operations.

  Many functions in the `DateTime` module require a time zone database.
  By default, this module uses the default time zone database returned by
  `Calendar.get_time_zone_database/0`, which defaults to
  `Calendar.UTCOnlyTimeZoneDatabase`. This database only handles `Etc/UTC`
  datetimes and returns `{:error, :utc_only_time_zone_database}`
  for any other time zone.

