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 civil Islamic {year, month, day} for the given ISO day number.

Arguments

• iso_days is an integer count of days since the proleptic ISO epoch.

Returns

• A three-tuple {year, month, day} in the civil Islamic calendar.

Examples

iex> Calendrical.Islamic.Civil.date_from_iso_days(739_252)
{1445, 6, 20}

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

Returns the number of ISO days for the given civil Islamic year, month, and day.

Arguments

• year is any Hijri year as an integer.

• month is a Hijri month in the range 1..12.

• day is a Hijri day-of-month in the range 1..30.

Returns

• An integer count of days since the proleptic ISO epoch.

Examples

iex> Calendrical.Islamic.Civil.date_to_iso_days(1447, 1, 1)
739794

@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 the number of days in the given Hijri year and month.

Odd-numbered months have 30 days and even-numbered months have 29 days, except month 12 (Dhū al-Ḥijjah) which has 30 days in a leap year.

Arguments

• year is any Hijri year as an integer.

• month is a Hijri month in the range 1..12.

Returns

• The number of days in the month (29 or 30).

Examples

iex> Calendrical.Islamic.Civil.days_in_month(1447, 1)
30

iex> Calendrical.Islamic.Civil.days_in_month(1446, 12)
29

iex> Calendrical.Islamic.Civil.days_in_month(1447, 12)
30

Returns the number days in a a week.

@spec days_in_year(year()) :: 354..355

Returns the number of days in the given Hijri year.

Arguments

• year is any Hijri year as an integer.

Returns

• 354 for an ordinary year or 355 for a leap year.

Examples

iex> Calendrical.Islamic.Civil.days_in_year(1446)
354

iex> Calendrical.Islamic.Civil.days_in_year(1447)
355

@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 leap_year?(year()) :: boolean()

Returns whether the given Hijri year is a leap year.

Leap years are determined by the Type II (Kūshyār) 30-year cycle in which years 2, 5, 7, 10, 13, 16, 18, 21, 24, 26 and 29 of each cycle are leap years.

Arguments

• year is any Hijri year as an integer.

Returns

• true if the year contains 355 days; otherwise false.

Examples

iex> Calendrical.Islamic.Civil.leap_year?(1447)
true

iex> Calendrical.Islamic.Civil.leap_year?(1446)
false

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 year, without a year.

Returns an integer when every year has the same number of months, or {:ambiguous, first..last} for lunisolar calendars whose year length varies (e.g. the Hebrew calendar's 12 or 13 months).

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 :years, :months, :weeks or :days.

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 Gregorian year as displayed on rendered calendars.

Per TR35 this is the Gregorian year in which this calendar's year begins, so it is constant for every date of the calendar year.

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.