Calendar behaviour

This module defines the responsibilities for working with calendars, dates, times and datetimes in Elixir.

Currently it defines types and the minimal implementation for a calendar behaviour in Elixir. The goal of the Calendar features in Elixir is to provide a base for interoperability instead of full-featured datetime API.

For the actual date, time and datetime structures, see Date, Time, NaiveDateTime and DateTime.

Note designations for year, month, day, and the like, are overspecified (i.e. an integer instead of 1..12 for months) because different calendars may have a different number of days per month, months per year and so on.

Summary

Types

calendar(): A calendar implementation
date(): Any map/struct that contains the date fields
datetime(): Any map/struct that contains the datetime fields
day()
day_fraction(): The internal time format is used when converting between calendars.
day_of_era(): A tuple representing the day and the era.
day_of_week()
era()
hour()
iso_days(): The internal date format that is used when converting between calendars.
microsecond(): Microseconds with stored precision.
minute()
month()
naive_datetime(): Any map/struct that contains the naive_datetime fields
second()
std_offset(): The time zone standard offset in seconds (not zero in summer times)
time(): Any map/struct that contains the time fields
time_zone(): The time zone ID according to the IANA tz database (for example, Europe/Zurich)
time_zone_database(): Specifies the time zone database for calendar operations.
utc_offset(): The time zone UTC offset in seconds
week()
year()
zone_abbr(): The time zone abbreviation (for example, CET or CEST or BST, and such)

Functions

compatible_calendars?(calendar, calendar): Returns true if two calendars have the same moment of starting a new day, false otherwise.
get_time_zone_database(): Gets the current time zone database.
put_time_zone_database(database): Sets the current time zone database.
truncate(microsecond_tuple, atom): Returns a microsecond tuple truncated to a given precision (:microsecond, :millisecond or :second).

Callbacks

date_to_string(year, month, day): Converts the date into a string according to the calendar.
datetime_to_string(year, month, day, hour, minute, second, microsecond, time_zone, zone_abbr, utc_offset, std_offset): Converts the datetime (with time zone) into a string according to the calendar.
day_of_era(year, month, day): Calculates the day and era from the given year, month, and day.
day_of_week(year, month, day): Calculates the day of the week from the given year, month, and day.
day_of_year(year, month, day): Calculates the day of the year from the given year, month, and day.
day_rollover_relative_to_midnight_utc(): Define the rollover moment for the given calendar.
days_in_month(year, month): Returns how many days there are in the given year-month.
leap_year?(year): Returns true if the given year is a leap year.
months_in_year(year): Returns how many months there are in the given year.
naive_datetime_from_iso_days(iso_days): Converts iso_days/0 to the Calendar's datetime format.
naive_datetime_to_iso_days(year, month, day, hour, minute, second, microsecond): Converts the given datetime (without time zone) into the iso_days/0 format.
naive_datetime_to_string(year, month, day, hour, minute, second, microsecond): Converts the datetime (without time zone) into a string according to the calendar.
parse_date(arg1): Parses the string representation for a date returned by date_to_string/3 into a date-tuple.
parse_naive_datetime(arg1): Parses the string representation for a naive datetime returned by naive_datetime_to_string/7 into a naive-datetime-tuple.
parse_time(arg1): Parses the string representation for a time returned by time_to_string/4 into a time-tuple.
parse_utc_datetime(arg1): Parses the string representation for a datetime returned by datetime_to_string/11 into a datetime-tuple.
quarter_of_year(year, month, day): Calculates the quarter of the year from the given year, month, and day.
time_from_day_fraction(day_fraction): Converts day_fraction/0 to the Calendar's time format.
time_to_day_fraction(hour, minute, second, microsecond): Converts the given time to the day_fraction/0 format.
time_to_string(hour, minute, second, microsecond): Converts the time into a string according to the calendar.
valid_date?(year, month, day): Should return true if the given date describes a proper date in the calendar.
valid_time?(hour, minute, second, microsecond): Should return true if the given time describes a proper time in the calendar.
year_of_era(year): Calculates the year and era from the given year.

Types

calendar()

Specs

calendar() :: module()

A calendar implementation

date()

Specs

date() :: %{
  optional(any()) => any(),
  :calendar => calendar(),
  :year => year(),
  :month => month(),
  :day => day()
}

Any map/struct that contains the date fields

datetime()

Specs

datetime() :: %{
  optional(any()) => any(),
  :calendar => calendar(),
  :year => year(),
  :month => month(),
  :day => day(),
  :hour => hour(),
  :minute => minute(),
  :second => second(),
  :microsecond => microsecond(),
  :time_zone => time_zone(),
  :zone_abbr => zone_abbr(),
  :utc_offset => utc_offset(),
  :std_offset => std_offset()
}

Any map/struct that contains the datetime fields

day()

Specs

day() :: pos_integer()

day_fraction()

Specs

day_fraction() ::
  {parts_in_day :: non_neg_integer(), parts_per_day :: pos_integer()}

The internal time format is used when converting between calendars.

It represents time as a fraction of a day (starting from midnight). parts_in_day specifies how much of the day is already passed, while parts_per_day signifies how many parts there fit in a day.

day_of_era()

Specs

day_of_era() :: {day :: non_neg_integer(), era()}

A tuple representing the day and the era.

day_of_week()

Specs

day_of_week() :: non_neg_integer()

era()

Specs

era() :: non_neg_integer()

hour()

Specs

hour() :: non_neg_integer()

iso_days()

Specs

iso_days() :: {days :: integer(), day_fraction()}

The internal date format that is used when converting between calendars.

This is the number of days including the fractional part that has passed of the last day since 0000-01-01+00:00T00:00.000000 in ISO 8601 notation (also known as midnight 1 January BC 1 of the proleptic Gregorian calendar).

microsecond()

Specs

microsecond() :: {non_neg_integer(), non_neg_integer()}

Microseconds with stored precision.

The precision represents the number of digits that must be used when representing the microseconds to external format. If the precision is 0, it means microseconds must be skipped.

minute()

Specs

minute() :: non_neg_integer()

month()

Specs

month() :: pos_integer()

naive_datetime()

Specs

naive_datetime() :: %{
  optional(any()) => any(),
  :calendar => calendar(),
  :year => year(),
  :month => month(),
  :day => day(),
  :hour => hour(),
  :minute => minute(),
  :second => second(),
  :microsecond => microsecond()
}

Any map/struct that contains the naive_datetime fields

second()

Specs

second() :: non_neg_integer()

std_offset()

Specs

std_offset() :: integer()

The time zone standard offset in seconds (not zero in summer times)

time()

Specs

time() :: %{
  optional(any()) => any(),
  :hour => hour(),
  :minute => minute(),
  :second => second(),
  :microsecond => microsecond()
}

Any map/struct that contains the time fields

time_zone()

Specs

time_zone() :: String.t()

The time zone ID according to the IANA tz database (for example, Europe/Zurich)

time_zone_database()

Specs

time_zone_database() :: module()

Specifies the time zone database for calendar operations.

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

Other time zone databases (including ones provided by packages) can be configured as default either via configuration:

config :elixir, :time_zone_database, CustomTimeZoneDatabase

or by calling Calendar.put_time_zone_database/1.

See Calendar.TimeZoneDatabase for more information on custom time zone databases.

utc_offset()

Specs

utc_offset() :: integer()

The time zone UTC offset in seconds

week()

Specs

week() :: pos_integer()

year()

Specs

year() :: integer()

zone_abbr()

Specs

zone_abbr() :: String.t()

The time zone abbreviation (for example, CET or CEST or BST, and such)

Functions

compatible_calendars?(calendar, calendar)

Specs

compatible_calendars?(calendar(), calendar()) :: boolean()

Returns true if two calendars have the same moment of starting a new day, false otherwise.

If two calendars are not compatible, we can only convert datetimes and times between them. If they are compatible, this means that we can also convert dates as well as naive datetimes between them.

get_time_zone_database()

Specs

get_time_zone_database() :: time_zone_database()

Gets the current time zone database.

put_time_zone_database(database)

Specs

put_time_zone_database(time_zone_database()) :: :ok

Sets the current time zone database.

truncate(microsecond_tuple, atom)

Specs

truncate(microsecond(), :microsecond | :millisecond | :second) :: microsecond()

Returns a microsecond tuple truncated to a given precision (:microsecond, :millisecond or :second).

Callbacks

date_to_string(year, month, day)

Specs

date_to_string(year(), month(), day()) :: String.t()

Converts the date into a string according to the calendar.

datetime_to_string(year, month, day, hour, minute, second, microsecond, time_zone, zone_abbr, utc_offset, std_offset)

Specs

datetime_to_string(
  year(),
  month(),
  day(),
  hour(),
  minute(),
  second(),
  microsecond(),
  time_zone(),
  zone_abbr(),
  utc_offset(),
  std_offset()
) :: String.t()

Converts the datetime (with time zone) into a string according to the calendar.

day_of_era(year, month, day)

Specs

day_of_era(year(), month(), day()) :: day_of_era()

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

day_of_week(year, month, day)

Specs

day_of_week(year(), month(), day()) :: day_of_week()

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

day_of_year(year, month, day)

Specs

day_of_year(year(), month(), day()) :: non_neg_integer()

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

day_rollover_relative_to_midnight_utc()

Specs

day_rollover_relative_to_midnight_utc() :: day_fraction()

Define the rollover moment for the given calendar.

This is the moment, in your calendar, when the current day ends and the next day starts.

The result of this function is used to check if two calendars rollover at the same time of day. If they do not, we can only convert datetimes and times between them. If they do, this means that we can also convert dates as well as naive datetimes between them.

This day fraction should be in its most simplified form possible, to make comparisons fast.

Examples

If, in your Calendar, a new day starts at midnight, return {0, 1}.
If, in your Calendar, a new day starts at sunrise, return {1, 4}.
If, in your Calendar, a new day starts at noon, return {1, 2}.
If, in your Calendar, a new day starts at sunset, return {3, 4}.

days_in_month(year, month)

Specs

days_in_month(year(), month()) :: day()

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

leap_year?(year)

Specs

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

Returns true if the given year is a leap year.

A leap year is a year of a longer length than normal. The exact meaning is up to the calendar. A calendar must return false if it does not support the concept of leap years.

months_in_year(year)

Specs

months_in_year(year()) :: month()

Returns how many months there are in the given year.

naive_datetime_from_iso_days(iso_days)

Specs

naive_datetime_from_iso_days(iso_days()) ::
  {year(), month(), day(), hour(), minute(), second(), microsecond()}

Converts iso_days/0 to the Calendar's datetime format.

naive_datetime_to_iso_days(year, month, day, hour, minute, second, microsecond)

Specs

naive_datetime_to_iso_days(
  year(),
  month(),
  day(),
  hour(),
  minute(),
  second(),
  microsecond()
) :: iso_days()

Converts the given datetime (without time zone) into the iso_days/0 format.

naive_datetime_to_string(year, month, day, hour, minute, second, microsecond)

Specs

naive_datetime_to_string(
  year(),
  month(),
  day(),
  hour(),
  minute(),
  second(),
  microsecond()
) :: String.t()

Converts the datetime (without time zone) into a string according to the calendar.

parse_date(arg1)

Specs

parse_date(String.t()) :: {:ok, {year(), month(), day()}} | {:error, atom()}

Parses the string representation for a date returned by date_to_string/3 into a date-tuple.

parse_naive_datetime(arg1)

Specs

parse_naive_datetime(String.t()) ::
  {:ok, {year(), month(), day(), hour(), minute(), second(), microsecond()}}
  | {:error, atom()}

Parses the string representation for a naive datetime returned by naive_datetime_to_string/7 into a naive-datetime-tuple.

The given string may contain a timezone offset but it is ignored.

parse_time(arg1)

Specs

parse_time(String.t()) ::
  {:ok, {hour(), minute(), second(), microsecond()}} | {:error, atom()}

Parses the string representation for a time returned by time_to_string/4 into a time-tuple.

parse_utc_datetime(arg1)

Specs

parse_utc_datetime(String.t()) ::
  {:ok, {year(), month(), day(), hour(), minute(), second(), microsecond()},
   utc_offset()}
  | {:error, atom()}

Parses the string representation for a datetime returned by 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.

quarter_of_year(year, month, day)

Specs

quarter_of_year(year(), month(), day()) :: non_neg_integer()

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

time_from_day_fraction(day_fraction)

Specs

time_from_day_fraction(day_fraction()) ::
  {hour(), minute(), second(), microsecond()}

Converts day_fraction/0 to the Calendar's time format.

time_to_day_fraction(hour, minute, second, microsecond)

Specs

time_to_day_fraction(hour(), minute(), second(), microsecond()) ::
  day_fraction()

Converts the given time to the day_fraction/0 format.

time_to_string(hour, minute, second, microsecond)

Specs

time_to_string(hour(), minute(), second(), microsecond()) :: String.t()

Converts the time into a string according to the calendar.

valid_date?(year, month, day)

Specs

valid_date?(year(), month(), day()) :: boolean()

Should return true if the given date describes a proper date in the calendar.

valid_time?(hour, minute, second, microsecond)

Specs

valid_time?(hour(), minute(), second(), microsecond()) :: boolean()

Should return true if the given time describes a proper time in the calendar.

year_of_era(year)

Specs

year_of_era(year()) :: {year(), era()}

Calculates the year and era from the given year.