Identifies whether this calendar is month or week based.

@spec calendar_year(Calendar.year(), Calendar.month(), Calendar.day()) ::
  Calendar.year()

Returns the calendar year as displayed on rendered calendars.

Defines the CLDR calendar type for this calendar.

This type is used in support of Calendrical. localize/3.

@spec cyclic_year(Calendar.year(), Calendar.month(), Calendar.day()) ::
  Calendar.year()

Returns the cyclic year as displayed on rendered calendars.

@spec date_from_iso_days(integer()) :: {year(), month(), day()}

Returns a Saudi sighting-based Islamic {year, month, day} for the given ISO day number.

@spec date_to_iso_days(year(), month(), day()) :: integer()

Returns the number of ISO days for the given Saudi sighting-based Islamic year, month, and day.

@spec day_of_era(Calendar.year(), Calendar.month(), Calendar.day()) ::
  {day :: Calendar.day(), era :: Calendar.era()}

Calculates the day and era from the given year, month, and day.

By default we consider on two eras: before the epoch and on-or-after the epoch.

@spec day_of_year(Calendar.year(), Calendar.month(), Calendar.day()) :: Calendar.day()

Calculates the day of the year from the given year, month, and day.

@spec days_in_month(Calendar.month()) ::
  Calendar.month()
  | {:ambiguous, Range.t() | [pos_integer()]}
  | {:error, :undefined}

Returns how many days there are in the given month.

Must be implemented in derived calendars because we cannot know what the calendar format is.

@spec days_in_month(Calendar.year(), Calendar.month()) :: Calendar.month()

@spec days_in_month(year(), month()) :: 29..30

Returns how many days there are in the given year and month.

Returns the number days in a a week.

Returns the number days in a given year.

The year is the number of years since the epoch.

@spec extended_year(Calendar.year(), Calendar.month(), Calendar.day()) ::
  Calendar.year()

Returns the extended year as displayed on rendered calendars.

@spec iso_week_of_year(Calendar.year(), Calendar.month(), Calendar.day()) ::
  {:error, :not_defined}

Calculates the ISO week of the year from the given year, month, and day.

By default this function always returns {:error, :not_defined}.

@spec location() :: Geo.PointZ.t()

Returns the geographic location used to determine crescent visibility for this calendar.

Returns a Date.Range.t/0 representing a given month of a year.

@spec month_of_year(Calendar.year(), Calendar.month(), Calendar.day()) ::
  Calendar.month() | {Calendar.month(), Calendrical.leap_month?()}

Returns the month of the year from the given year, month, and day.

Returns the number of months in a leap year.

Returns the number of months in a normal year.

Returns the number of months in a given year.

@spec naive_datetime_from_iso_days(Calendar.iso_days()) ::
  {Calendar.year(), Calendar.month(), Calendar.day(), Calendar.hour(),
   Calendar.minute(), Calendar.second(), Calendar.microsecond()}

Converts the t:Calendar.iso_days format to the datetime format specified by this calendar.

@spec naive_datetime_to_iso_days(
  Calendar.year(),
  Calendar.month(),
  Calendar.day(),
  Calendar.hour(),
  Calendar.minute(),
  Calendar.second(),
  Calendar.microsecond()
) :: Calendar.iso_days()

Returns the t:Calendar.iso_days format of the specified date.

Returns the number of periods in a given year. A period corresponds to a month in month-based calendars and a week in week-based calendars.

Adds an increment number of date_parts to a year-month-day.

date_part can be :months only.

Returns a Date.Range.t/0 representing a given quarter of a year.

@spec quarter_of_year(Calendar.year(), Calendar.month(), Calendar.day()) ::
  Calendrical.quarter()

Returns the quarter of the year from the given year, month, and day.

@spec related_gregorian_year(Calendar.year(), Calendar.month(), Calendar.day()) ::
  Calendar.year()

Returns the related gregorain year as displayed on rendered calendars.

Determines if the date given is valid according to this calendar.

Returns a Date.Range.t/0 representing a given week of a year.

@spec week_of_month(Calendar.year(), Calendar.month(), Calendar.day()) ::
  {pos_integer(), pos_integer()} | {:error, :not_defined}

Calculates the week of the year from the given year, month, and day.

By default this function always returns {:error, :not_defined}.

@spec week_of_year(Calendar.year(), Calendar.month(), Calendar.day()) ::
  {:error, :not_defined}

Calculates the week of the year from the given year, month, and day.

By default this function always returns {:error, :not_defined}.

Returns the number of weeks in a given year.

Returns a Date.Range.t/0 representing a given year.

@spec year_of_era(Calendar.year()) :: {year :: Calendar.year(), era :: Calendar.era()}

Calculates the year and era from the given year.

@spec year_of_era(Calendar.year(), Calendar.month(), Calendar.day()) ::
  {year :: Calendar.year(), era :: Calendar.era()}

Calculates the year and era from the given date.