Elixir v1.11.0-dev Calendar behaviour View Source

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.

Link to this section Summary

Types

A calendar implementation

Any map/struct that contains the date fields

Any map/struct that contains the datetime fields

The internal time format is used when converting between calendars.

A tuple representing the day and the era.

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

Microseconds with stored precision.

Any map/struct that contains the naive_datetime fields

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

Any map/struct that contains the time fields

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

Specifies the time zone database for calendar operations.

The time zone UTC offset in seconds

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

Functions

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

Gets the current time zone database.

Sets the current time zone database.

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

Callbacks

Converts the date into a string according to the calendar.

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

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

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

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

Define the rollover moment for the given calendar.

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

Returns true if the given year is a leap year.

Returns how many months there are in the given year.

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

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

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

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

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

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

Parses the string representation for a datetime returned by datetime_to_string/11 into a datetime-tuple.

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

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

Converts the time into a string according to the calendar.

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

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

Calculates the year and era from the given year.

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calendar()

View Source
calendar() :: module()

A calendar implementation

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date()

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

Any map/struct that contains the date fields

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datetime()

View Source
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

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day_fraction()

View Source
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.

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day_of_era()

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

A tuple representing the day and the era.

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day_of_week()

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day_of_week() :: non_neg_integer()
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iso_days()

View Source
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).

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.

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naive_datetime()

View Source
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

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std_offset()

View Source
std_offset() :: integer()

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

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time()

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

Any map/struct that contains the time fields

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time_zone()

View Source
time_zone() :: String.t()

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

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time_zone_database()

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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.

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utc_offset()

View Source
utc_offset() :: integer()

The time zone UTC offset in seconds

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zone_abbr()

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zone_abbr() :: String.t()

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

Link to this section Functions

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compatible_calendars?(calendar, calendar)

View Source (since 1.5.0)
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.

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get_time_zone_database()

View Source (since 1.8.0)
get_time_zone_database() :: time_zone_database()

Gets the current time zone database.

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put_time_zone_database(database)

View Source (since 1.8.0)
put_time_zone_database(time_zone_database()) :: :ok

Sets the current time zone database.

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strftime(date_or_time_or_datetime, string_format, user_options \\ [])

View Source (since 1.11.0)
strftime(map(), String.t(), keyword()) :: String.t()

Formats received datetime into a string.

The datetime can be any of the Calendar types (Time, Date, NaiveDateTime, and DateTime) or any map, as long as they contain all of the relevant fields necessary for formatting. For example, if you use %Y to format the year, the datetime must have the :year field. Therefore, if you pass a Time, or a map without the :year field to a format that expects %Y, an error will be raised.

Options

  • :preferred_datetime - a string for the preferred format to show datetimes, it can't contain the %c format and defaults to "%Y-%m-%d %H:%M:%S" if the option is not received

  • :preferred_date - a string for the preferred format to show dates, it can't contain the %x format and defaults to "%Y-%m-%d" if the option is not received

  • :preferred_time - a string for the preferred format to show times, it can't contain the %X format and defaults to "%H:%M:%S" if the option is not received

  • :am_pm_names - a function that receives either :am or :pm and returns the name of the period of the day, if the option is not received it defaults to a function that returns "am" and "pm", respectively

  • :month_names - a function that receives a number and returns the name of the corresponding month, if the option is not received it defaults to a function thet returns the month names in english

  • :abbreviated_month_names - a function that receives a number and returns the abbreviated name of the corresponding month, if the option is not received it defaults to a function thet returns the abbreviated month names in english

  • :day_of_week_names - a function that receives a number and returns the name of the corresponding day of week, if the option is not received it defaults to a function that returns the day of week names in english

  • :abbreviated_day_of_week_names - a function that receives a number and returns the abbreviated name of the corresponding day of week, if the option is not received it defaults to a function that returns the abbreviated day of week names in english

Formatting syntax

The formatting syntax for strftime is a sequence of characters in the following format:

%<padding><width><format>

where:

  • %: indicates the start of a formatted section
  • <padding>: set the padding (see below)
  • <width>: a number indicating the minimum size of the formatted section
  • <format>: the format iself (see below)

Accepted padding options

  • -: no padding, removes all padding from the format
  • _: pad with spaces
  • 0: pad with zeroes

Accepted formats

The accepted formats are:

FormatDescriptionExamples (in ISO)
aAbbreviated name of dayMon
AFull name of dayMonday
bAbbreviated month nameJan
BFull month nameJanuary
cPreferred date+time representation2018-10-17 12:34:56
dDay of the month01, 12
fMicroseconds (does not support width and padding modifiers)000000, 999999, 0123
HHour using a 24-hour clock00, 23
IHour using a 12-hour clock01, 12
jDay of the year001, 366
mMonth01, 12
MMinute00, 59
p"AM" or "PM" (noon is "PM", midnight as "AM")AM, PM
P"am" or "pm" (noon is "pm", midnight as "am")am, pm
qQuarter1, 2, 3, 4
SSecond00, 59, 60
uDay of the week1 (Monday), 7 (Sunday)
xPreferred date (without time) representation2018-10-17
XPreferred time (without date) representation12:34:56
yYear as 2-digits01, 01, 86, 18
YYear-0001, 0001, 1986
z+hhmm/-hhmm time zone offset from UTC (empty string if naive)+0300, -0530
ZTime zone abbreviation (empty string if naive)CET, BRST
%Literal "%" character%

Any other character will be interpreted as an invalid format and raise an error

Examples

Without options:

iex> Calendar.strftime(~U[2019-08-26 13:52:06.0Z], "%y-%m-%d %I:%M:%S %p")
"19-08-26 01:52:06 PM"

iex> Calendar.strftime(~U[2019-08-26 13:52:06.0Z], "%a, %B %d %Y")
"Mon, August 26 2019"

iex> Calendar.strftime(~U[2019-08-26 13:52:06.0Z], "%c")
"2019-08-26 13:52:06"

With options:

iex> Calendar.strftime(~U[2019-08-26 13:52:06.0Z], "%c", preferred_datetime: "%H:%M:%S %d-%m-%y")
"13:52:06 26-08-19"

iex> Calendar.strftime(
...>  ~U[2019-08-26 13:52:06.0Z],
...>  "%A",
...>  day_of_week_names: fn day_of_week ->
...>    {"segunda-feira", "terça-feira", "quarta-feira", "quinta-feira",
...>    "sexta-feira", "sábado", "domingo"}
...>    |> elem(day_of_week - 1)
...>  end
...>)
"segunda-feira"

iex> Calendar.strftime(
...>  ~U[2019-08-26 13:52:06.0Z],
...>  "%B",
...>  month_names: fn month ->
...>    {"январь", "февраль", "март", "апрель", "май", "июнь",
...>    "июль", "август", "сентябрь", "октябрь", "ноябрь", "декабрь"}
...>    |> elem(month - 1)
...>  end
...>)
"август"
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truncate(microsecond_tuple, atom)

View Source (since 1.6.0)
truncate(microsecond(), :microsecond | :millisecond | :second) :: microsecond()

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

Link to this section Callbacks

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date_to_string(year, month, day)

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

Converts the date into a string according to the calendar.

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

View Source
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.

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day_of_era(year, month, day)

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

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

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day_of_week(year, month, day)

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

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

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day_of_year(year, month, day)

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

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

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day_rollover_relative_to_midnight_utc()

View Source
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}.
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days_in_month(year, month)

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

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

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leap_year?(year)

View Source
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.

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months_in_year(year)

View Source
months_in_year(year()) :: month()

Returns how many months there are in the given year.

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naive_datetime_from_iso_days(iso_days)

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

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

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

View Source
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.

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

View Source
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.

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parse_date(arg1)

View Source (since 1.10.0)
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.

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parse_naive_datetime(arg1)

View Source (since 1.10.0)
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.

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parse_time(arg1)

View Source (since 1.10.0)
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.

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parse_utc_datetime(arg1)

View Source (since 1.10.0)
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.

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quarter_of_year(year, month, day)

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

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

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time_from_day_fraction(day_fraction)

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

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

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time_to_day_fraction(hour, minute, second, microsecond)

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

Converts the given time to the day_fraction/0 format.

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time_to_string(hour, minute, second, microsecond)

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

Converts the time into a string according to the calendar.

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valid_date?(year, month, day)

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

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

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valid_time?(hour, minute, second, microsecond)

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

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

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year_of_era(year)

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

Calculates the year and era from the given year.