# `Calendrical.Ethiopic.AmeteAlem` Implementation of the Ethiopic calendar with the *Amete Alem* (Era of the World, *Anno Mundi*) year numbering. This calendar is structurally identical to `Calendrical.Ethiopic` — same 13-month layout, same leap-year rule, same days-in-month — but the year is counted from the traditional Ethiopian Christian date of the creation of the world rather than from the Era of Mercy: amete_alem_year = amete_mihret_year + 5500 So 1 Amete Alem = -5499 Julian = -5492-07-17 proleptic Gregorian (per CLDR era data) and modern Ethiopic year 2017 (Amete Mihret) = 7517 Amete Alem. Days are assumed to begin at midnight rather than at sunset. ## Reference - Dershowitz & Reingold, *Calendrical Calculations* (4th ed.), §4.2 ("Ethiopic and Coptic Calendars"). - CLDR `:ethiopic_amete_alem` calendar type. The CLDR era data places the *aa* era at proleptic Gregorian `-5492-07-17`. See `Calendrical.Ethiopic` for the month structure and the `mod(year, 4) == 3` leap-year rule. # `day` ```elixir @type day() :: 1..30 ``` # `month` ```elixir @type month() :: 1..13 ``` # `year` ```elixir @type year() :: integer() ``` # `amete_alem_year` ```elixir @spec amete_alem_year(integer()) :: year() ``` Returns the Amete Alem year for the given Amete Mihret (`Calendrical.Ethiopic`) year. ### Arguments * `amete_mihret_year` is any Amete Mihret (Ethiopic) year as an integer. ### Returns * An integer Amete Alem year (5500 more than the input). ### Examples iex> Calendrical.Ethiopic.AmeteAlem.amete_alem_year(2018) 7518 # `amete_mihret_year` ```elixir @spec amete_mihret_year(year()) :: integer() ``` Returns the corresponding `Calendrical.Ethiopic` (Amete Mihret) year for the given Amete Alem year. ### Arguments * `amete_alem_year` is any Amete Alem year as an integer. ### Returns * An integer Amete Mihret year (5500 less than the input). ### Examples iex> Calendrical.Ethiopic.AmeteAlem.amete_mihret_year(7518) 2018 # `calendar_base` Identifies whether this calendar is month or week based. # `calendar_year` ```elixir @spec calendar_year(Calendar.year(), Calendar.month(), Calendar.day()) :: Calendar.year() ``` Returns the calendar year as displayed on rendered calendars. # `cldr_calendar_type` Defines the CLDR calendar type for this calendar. This type is used in support of `Calendrical. localize/3`. # `cyclic_year` ```elixir @spec cyclic_year(Calendar.year(), Calendar.month(), Calendar.day()) :: Calendar.year() ``` Returns the cyclic year as displayed on rendered calendars. # `date_from_iso_days` ```elixir @spec date_from_iso_days(integer()) :: {year(), month(), day()} ``` Returns an Amete Alem `{year, month, day}` tuple 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 Amete Alem numbering. ### Examples iex> Calendrical.Ethiopic.AmeteAlem.date_from_iso_days(740_000) {7518, 5, 11} # `date_to_iso_days` ```elixir @spec date_to_iso_days(year(), month(), day()) :: integer() ``` Returns the number of ISO days for the given Amete Alem `year`, `month`, and `day`. ### Arguments * `year` is any Amete Alem year as an integer. * `month` is an Ethiopic month in the range `1..13`. * `day` is an Ethiopic day-of-month. ### Returns * An integer count of days since the proleptic ISO epoch. ### Examples iex> Calendrical.Ethiopic.AmeteAlem.date_to_iso_days(7518, 1, 1) 739870 # `day_of_era` ```elixir @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. # `day_of_week` ```elixir @spec day_of_week( Calendar.year(), Calendar.month(), Calendar.day(), :default | atom() ) :: {Calendar.day_of_week(), first_day_of_week :: non_neg_integer(), last_day_of_week :: non_neg_integer()} @spec day_of_week(year(), month(), day(), :default) :: {1..7, 6, 5} ``` Returns the day of the week for the given Amete Alem `year`, `month`, and `day`. Ethiopic weeks begin on Saturday, so the returned tuple has `first_day_of_week = 6` and `last_day_of_week = 5`. ### Arguments * `year` is any Amete Alem year as an integer. * `month` is an Ethiopic month in the range `1..13`. * `day` is an Ethiopic day-of-month. * `starting_on` is `:default` for the calendar's natural week boundary (Saturday). ### Returns * A three-tuple `{day_of_week, first_day_of_week, last_day_of_week}`. ### Examples iex> Calendrical.Ethiopic.AmeteAlem.day_of_week(7518, 1, 1, :default) {4, 6, 5} # `day_of_year` ```elixir @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`. # `days_in_month` ```elixir @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. # `days_in_month` ```elixir @spec days_in_month(Calendar.year(), Calendar.month()) :: Calendar.month() @spec days_in_month(year(), month()) :: 5..30 ``` Returns the number of days in the given Amete Alem `year` and `month`. Months 1-12 always have 30 days; month 13 has 5 days, or 6 in a leap year. ### Arguments * `year` is any Amete Alem year as an integer. * `month` is an Ethiopic month in the range `1..13`. ### Returns * An integer number of days. ### Examples iex> Calendrical.Ethiopic.AmeteAlem.days_in_month(7518, 13) 5 iex> Calendrical.Ethiopic.AmeteAlem.days_in_month(7519, 13) 6 # `days_in_week` Returns the number days in a a week. # `days_in_year` ```elixir @spec days_in_year(year()) :: 365..366 ``` Returns the number of days in the given Amete Alem `year`. ### Arguments * `year` is any Amete Alem year as an integer. ### Returns * `365` for an ordinary year or `366` for a leap year. ### Examples iex> Calendrical.Ethiopic.AmeteAlem.days_in_year(7518) 365 iex> Calendrical.Ethiopic.AmeteAlem.days_in_year(7519) 366 # `epoch` # `epoch_day_of_week` # `era_offset` ```elixir @spec era_offset() :: 5500 ``` Returns the offset (in years) between the Amete Alem (Era of the World) and the Amete Mihret (Era of Mercy) used by `Calendrical.Ethiopic`. Subtracting this offset from an Amete Alem year yields the corresponding Amete Mihret year. ### Returns * The integer `5500`. ### Examples iex> Calendrical.Ethiopic.AmeteAlem.era_offset() 5500 # `extended_year` ```elixir @spec extended_year(Calendar.year(), Calendar.month(), Calendar.day()) :: Calendar.year() ``` Returns the extended year as displayed on rendered calendars. # `first_day_of_week` # `iso_week_of_year` ```elixir @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}`. # `last_day_of_week` # `leap_year?` ```elixir @spec leap_year?(year()) :: boolean() ``` Returns whether the given Amete Alem `year` is a leap year. The leap-year rule is that of `Calendrical.Ethiopic` applied to the corresponding Amete Mihret year. ### Arguments * `year` is any Amete Alem year as an integer. ### Returns * `true` if the year contains 366 days; otherwise `false`. ### Examples iex> Calendrical.Ethiopic.AmeteAlem.leap_year?(7519) true iex> Calendrical.Ethiopic.AmeteAlem.leap_year?(7518) false # `month` Returns a `t:Date.Range.t/0` representing a given month of a year. # `month_of_year` ```elixir @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`. # `months_in_leap_year` Returns the number of months in a leap year. # `months_in_ordinary_year` Returns the number of months in a normal year. # `months_in_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). # `months_in_year` Returns the number of months in a given `year`. # `naive_datetime_from_iso_days` ```elixir @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. # `naive_datetime_to_iso_days` ```elixir @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. # `periods_in_year` 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. # `plus` Adds an `increment` number of `date_part`s to a `year-month-day`. `date_part` can be `:years`, `:months`, `:weeks` or `:days`. # `quarter` Returns a `t:Date.Range.t/0` representing a given quarter of a year. # `quarter_of_year` ```elixir @spec quarter_of_year(Calendar.year(), Calendar.month(), Calendar.day()) :: Calendrical.quarter() ``` Returns `{:error, :not_defined}` because the Ethiopic calendar does not define quarters; the year has 13 months and so does not divide evenly into four quarters. ### Arguments * `year` is any Amete Alem year as an integer. * `month` is an Ethiopic month in the range `1..13`. * `day` is an Ethiopic day-of-month. ### Returns * `{:error, :not_defined}`. ### Examples iex> Calendrical.Ethiopic.AmeteAlem.quarter_of_year(7518, 1, 1) {:error, :not_defined} # `related_gregorian_year` ```elixir @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. # `valid_date?` ```elixir @spec valid_date?(year(), month(), day()) :: boolean() ``` Returns whether the given `year`, `month`, and `day` form a valid Amete Alem date. ### Arguments * `year` is any Amete Alem year as an integer. * `month` is an Ethiopic month in the range `1..13`. * `day` is an Ethiopic day-of-month. Months `1..12` have 30 days; month 13 has 5 days, or 6 in a leap year. ### Returns * `true` if the date is valid; otherwise `false`. ### Examples iex> Calendrical.Ethiopic.AmeteAlem.valid_date?(7518, 1, 30) true iex> Calendrical.Ethiopic.AmeteAlem.valid_date?(7519, 13, 6) true iex> Calendrical.Ethiopic.AmeteAlem.valid_date?(7518, 13, 6) false # `week` Returns a `t:Date.Range.t/0` representing a given week of a year. # `week_of_month` ```elixir @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}`. # `week_of_year` ```elixir @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}`. # `weeks_in_year` Returns the number of weeks in a given `year`. # `year` Returns a `t:Date.Range.t/0` representing a given year. # `year_of_era` ```elixir @spec year_of_era(Calendar.year()) :: {year :: Calendar.year(), era :: Calendar.era()} ``` Calculates the year and era from the given `year`. # `year_of_era` ```elixir @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`. --- *Consult [api-reference.md](api-reference.md) for complete listing*