Calendar.ISO — Elixir v1.16.3

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# View Source Calendar.ISO (Elixir v1.16.3)

The default calendar implementation, a Gregorian calendar following ISO 8601.

This calendar implements a proleptic Gregorian calendar and is therefore compatible with the calendar used in most countries today. The proleptic means the Gregorian rules for leap years are applied for all time, consequently the dates give different results before the year 1583 from when the Gregorian calendar was adopted.

## ISO 8601 compliance

The ISO 8601 specification is feature-rich, but allows applications to selectively implement most parts of it. The choices Elixir makes are catalogued below.

### Features

The standard library supports a minimal set of possible ISO 8601 features. Specifically, the parser only supports calendar dates and does not support ordinal and week formats.

By default Elixir only parses extended-formatted date/times. You can opt-in to parse basic-formatted date/times.

`NaiveDateTime.to_iso8601/2` and `DateTime.to_iso8601/2` allow you to produce either basic or extended formatted strings, and `Calendar.strftime/2` allows you to format datetimes however else you desire.

Elixir does not support reduced accuracy formats (for example, a date without the day component) nor decimal precisions in the lowest component (such as `10:01:25,5`). No functions exist to parse ISO 8601 durations or time intervals.

#### Examples

Elixir expects the extended format by default when parsing:

    iex> Calendar.ISO.parse_naive_datetime("2015-01-23T23:50:07")
    {:ok, {2015, 1, 23, 23, 50, 7, {0, 0}}}
    iex> Calendar.ISO.parse_naive_datetime("20150123T235007")
    {:error, :invalid_format}

Parsing can be restricted to basic if desired:

    iex> Calendar.ISO.parse_naive_datetime("20150123T235007Z", :basic)
    {:ok, {2015, 1, 23, 23, 50, 7, {0, 0}}}
    iex> Calendar.ISO.parse_naive_datetime("20150123T235007Z", :extended)
    {:error, :invalid_format}

Only calendar dates are supported in parsing; ordinal and week dates are not.

    iex> Calendar.ISO.parse_date("2015-04-15")
    {:ok, {2015, 4, 15}}
    iex> Calendar.ISO.parse_date("2015-105")
    {:error, :invalid_format}
    iex> Calendar.ISO.parse_date("2015-W16")
    {:error, :invalid_format}
    iex> Calendar.ISO.parse_date("2015-W016-3")
    {:error, :invalid_format}

Years, months, days, hours, minutes, and seconds must be fully specified:

    iex> Calendar.ISO.parse_date("2015-04-15")
    {:ok, {2015, 4, 15}}
    iex> Calendar.ISO.parse_date("2015-04")
    {:error, :invalid_format}
    iex> Calendar.ISO.parse_date("2015")
    {:error, :invalid_format}

    iex> Calendar.ISO.parse_time("23:50:07.0123456")
    {:ok, {23, 50, 7, {12345, 6}}}
    iex> Calendar.ISO.parse_time("23:50:07")
    {:ok, {23, 50, 7, {0, 0}}}
    iex> Calendar.ISO.parse_time("23:50")
    {:error, :invalid_format}
    iex> Calendar.ISO.parse_time("23")
    {:error, :invalid_format}

### Extensions

The parser and formatter adopt one ISO 8601 extension: extended year notation.

This allows dates to be prefixed with a `+` or `-` sign, extending the range of expressible years from the default (`0000..9999`) to `-9999..9999`. Elixir still restricts years in this format to four digits.

#### Examples

    iex> Calendar.ISO.parse_date("-2015-01-23")
    {:ok, {-2015, 1, 23}}
    iex> Calendar.ISO.parse_date("+2015-01-23")
    {:ok, {2015, 1, 23}}

    iex> Calendar.ISO.parse_naive_datetime("-2015-01-23 23:50:07")
    {:ok, {-2015, 1, 23, 23, 50, 7, {0, 0}}}
    iex> Calendar.ISO.parse_naive_datetime("+2015-01-23 23:50:07")
    {:ok, {2015, 1, 23, 23, 50, 7, {0, 0}}}

    iex> Calendar.ISO.parse_utc_datetime("-2015-01-23 23:50:07Z")
    {:ok, {-2015, 1, 23, 23, 50, 7, {0, 0}}, 0}
    iex> Calendar.ISO.parse_utc_datetime("+2015-01-23 23:50:07Z")
    {:ok, {2015, 1, 23, 23, 50, 7, {0, 0}}, 0}

### Additions

ISO 8601 does not allow a whitespace instead of `T` as a separator between date and times, both when parsing and formatting. This is a common enough representation, Elixir allows it during parsing.

The formatting of dates in `NaiveDateTime.to_iso8601/1` and `DateTime.to_iso8601/1` do produce specification-compliant string representations using the `T` separator.

#### Examples

    iex> Calendar.ISO.parse_naive_datetime("2015-01-23 23:50:07.0123456")
    {:ok, {2015, 1, 23, 23, 50, 7, {12345, 6}}}
    iex> Calendar.ISO.parse_naive_datetime("2015-01-23T23:50:07.0123456")
    {:ok, {2015, 1, 23, 23, 50, 7, {12345, 6}}}

    iex> Calendar.ISO.parse_utc_datetime("2015-01-23 23:50:07.0123456Z")
    {:ok, {2015, 1, 23, 23, 50, 7, {12345, 6}}, 0}
    iex> Calendar.ISO.parse_utc_datetime("2015-01-23T23:50:07.0123456Z")
    {:ok, {2015, 1, 23, 23, 50, 7, {12345, 6}}, 0}

# Summary

## Types

bce()

"Before the Current Era" or "Before the Common Era" (BCE), for those years less than `1`.

ce()

The "Current Era" or the "Common Era" (CE) which starts in year `1`.

day()
day_of_week()

Integer that represents the day of the week, where 1 is Monday and 7 is Sunday.

day_of_year()
era()

The calendar era.

format()
hour()
microsecond()

Microseconds with stored precision.

minute()
month()
quarter_of_year()
second()
utc_offset()
weekday()
year()
year_of_era()

## Functions

date_to_string(year, month, day, format \\ :extended)

Converts the given date into a string.

datetime_to_string(year, month, day, hour, minute, second, microsecond, time_zone, zone_abbr, utc_offset, std_offset, format \\ :extended)

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

day_of_era(year, month, day)

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

day_of_week(year, month, day, starting_on)

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()

See `Calendar.day_rollover_relative_to_midnight_utc/0` for documentation.

days_in_month(year, month)

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

iso_days_to_beginning_of_day(arg)

Converts the `Calendar.iso_days/0` to the first moment of the day.

iso_days_to_end_of_day(arg)

Converts the `Calendar.iso_days/0` to the last moment of the day.

leap_year?(year)

Returns 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(arg)

Converts the `Calendar.iso_days/0` format to the datetime format specified by this calendar.

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

Returns the `Calendar.iso_days/0` format of the specified date.

naive_datetime_to_string(year, month, day, hour, minute, second, microsecond, format \\ :extended)

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

parse_date(string)

Parses a date `string` in the `:extended` format.

parse_date(string, format)

Parses a date `string` according to a given `format`.

parse_naive_datetime(string)

Parses a naive datetime `string` in the `:extended` format.

parse_naive_datetime(string, format)

Parses a naive datetime `string` according to a given `format`.

parse_time(string)

Parses a time `string` in the `:extended` format.

parse_time(string, format)

Parses a time `string` according to a given `format`.

parse_utc_datetime(string)

Parses a UTC datetime `string` in the `:extended` format.

parse_utc_datetime(string, format)

Parses a UTC datetime `string` according to a given `format`.

quarter_of_year(year, month, day)

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

time_from_day_fraction(arg)

Converts a day fraction to this Calendar's representation of time.

time_to_day_fraction(hour, minute, second, arg)

Returns the normalized day fraction of the specified time.

time_to_string(hour, minute, second, microsecond, format \\ :extended)

Converts the given time into a string.

time_unit_to_precision(int)

Converts a `System.time_unit/0` to precision.

valid_date?(year, month, day)

Determines if the date given is valid according to the proleptic Gregorian calendar.

valid_time?(hour, minute, second, microsecond)

Determines if the date given is valid according to the proleptic Gregorian calendar.

year_of_era(year)

Calculates the year and era from the given `year`.

year_of_era(year, month, day)

Calendar callback to compute the year and era from the given `year`, `month` and `day`.

# Types

Link to this type

# bce()

View Source

    @type bce() :: 0

"Before the Current Era" or "Before the Common Era" (BCE), for those years less than `1`.

Link to this type

# ce()

View Source

    @type ce() :: 1

The "Current Era" or the "Common Era" (CE) which starts in year `1`.

Link to this type

# day()

View Source

    @type day() :: 1..31

Link to this type

# day_of_week()

View Source

    @type day_of_week() :: 1..7

Integer that represents the day of the week, where 1 is Monday and 7 is Sunday.

Link to this type

# day_of_year()

View Source

    @type day_of_year() :: 1..366

Link to this type

# era()

View Source

    @type era() :: bce() | ce()

The calendar era.

The ISO calendar has two eras:

- CE - which starts in year `1` and is defined as era `1`.
- BCE - for those years less than `1` and is defined as era `0`.

Link to this type

# format()

View Source

    @type format() :: :basic | :extended

Link to this type

# hour()

View Source

    @type hour() :: 0..23

Link to this type

# microsecond()

View Source

    @type microsecond() :: {0..999_999, 0..6}

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.

Link to this type

# minute()

View Source

    @type minute() :: 0..59

Link to this type

# month()

View Source

    @type month() :: 1..12

Link to this type

# quarter_of_year()

View Source

    @type quarter_of_year() :: 1..4

Link to this type

# second()

View Source

    @type second() :: 0..59

Link to this type

# utc_offset()

View Source

    @type utc_offset() :: integer()

Link to this type

# weekday()

View Source

    @type weekday() ::
      :monday | :tuesday | :wednesday | :thursday | :friday | :saturday | :sunday

Link to this type

# year()

View Source

    @type year() :: -9999..9999

Link to this type

# year_of_era()

View Source

    @type year_of_era() :: {1..10000, era()}

# Functions

Link to this function

# date_to_string(year, month, day, format \\ :extended)

View Source (since 1.4.0)

    @spec date_to_string(year(), month(), day(), :basic | :extended) :: String.t()

Converts the given date into a string.

By default, returns dates formatted in the "extended" format, for human readability. It also supports the "basic" format by passing the `:basic` option.

## Examples

    iex> Calendar.ISO.date_to_string(2015, 2, 28)
    "2015-02-28"
    iex> Calendar.ISO.date_to_string(2017, 8, 1)
    "2017-08-01"
    iex> Calendar.ISO.date_to_string(-99, 1, 31)
    "-0099-01-31"

    iex> Calendar.ISO.date_to_string(2015, 2, 28, :basic)
    "20150228"
    iex> Calendar.ISO.date_to_string(-99, 1, 31, :basic)
    "-00990131"

Link to this function

# datetime_to_string(year, month, day, hour, minute, second, microsecond, time_zone, zone_abbr, utc_offset, std_offset, format \\ :extended)

View Source (since 1.4.0)

    @spec datetime_to_string(
      year(),
      month(),
      day(),
      Calendar.hour(),
      Calendar.minute(),
      Calendar.second(),
      Calendar.microsecond(),
      Calendar.time_zone(),
      Calendar.zone_abbr(),
      Calendar.utc_offset(),
      Calendar.std_offset(),
      :basic | :extended
    ) :: String.t()

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

By default, returns datetimes formatted in the "extended" format, for human readability. It also supports the "basic" format by passing the `:basic` option.

## Examples

    iex> time_zone = "Etc/UTC"
    iex> Calendar.ISO.datetime_to_string(2017, 8, 1, 1, 2, 3, {4, 5}, time_zone, "UTC", 0, 0)
    "2017-08-01 01:02:03.00000Z"
    iex> Calendar.ISO.datetime_to_string(2017, 8, 1, 1, 2, 3, {4, 5}, time_zone, "UTC", 3600, 0)
    "2017-08-01 01:02:03.00000+01:00"
    iex> Calendar.ISO.datetime_to_string(2017, 8, 1, 1, 2, 3, {4, 5}, time_zone, "UTC", 3600, 3600)
    "2017-08-01 01:02:03.00000+02:00"

    iex> time_zone = "Europe/Berlin"
    iex> Calendar.ISO.datetime_to_string(2017, 8, 1, 1, 2, 3, {4, 5}, time_zone, "CET", 3600, 0)
    "2017-08-01 01:02:03.00000+01:00 CET Europe/Berlin"
    iex> Calendar.ISO.datetime_to_string(2017, 8, 1, 1, 2, 3, {4, 5}, time_zone, "CDT", 3600, 3600)
    "2017-08-01 01:02:03.00000+02:00 CDT Europe/Berlin"

    iex> time_zone = "America/Los_Angeles"
    iex> Calendar.ISO.datetime_to_string(2015, 2, 28, 1, 2, 3, {4, 5}, time_zone, "PST", -28800, 0)
    "2015-02-28 01:02:03.00000-08:00 PST America/Los_Angeles"
    iex> Calendar.ISO.datetime_to_string(2015, 2, 28, 1, 2, 3, {4, 5}, time_zone, "PDT", -28800, 3600)
    "2015-02-28 01:02:03.00000-07:00 PDT America/Los_Angeles"

    iex> time_zone = "Europe/Berlin"
    iex> Calendar.ISO.datetime_to_string(2017, 8, 1, 1, 2, 3, {4, 5}, time_zone, "CET", 3600, 0, :basic)
    "20170801 010203.00000+0100 CET Europe/Berlin"

Link to this function

# day_of_era(year, month, day)

View Source (since 1.8.0)

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

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

## Examples

    iex> Calendar.ISO.day_of_era(0, 1, 1)
    {366, 0}
    iex> Calendar.ISO.day_of_era(1, 1, 1)
    {1, 1}
    iex> Calendar.ISO.day_of_era(0, 12, 31)
    {1, 0}
    iex> Calendar.ISO.day_of_era(0, 12, 30)
    {2, 0}
    iex> Calendar.ISO.day_of_era(-1, 12, 31)
    {367, 0}

Link to this function

# day_of_week(year, month, day, starting_on)

View Source (since 1.11.0)

    @spec day_of_week(year(), month(), day(), :default | weekday()) ::
      {day_of_week(), 1, 7}

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

It is an integer from 1 to 7, where 1 is the given `starting_on` weekday. For example, if `starting_on` is set to `:monday`, then 1 is Monday and 7 is Sunday.

`starting_on` can also be `:default`, which is equivalent to `:monday`.

## Examples

    iex> Calendar.ISO.day_of_week(2016, 10, 31, :monday)
    {1, 1, 7}
    iex> Calendar.ISO.day_of_week(2016, 11, 1, :monday)
    {2, 1, 7}
    iex> Calendar.ISO.day_of_week(2016, 11, 2, :monday)
    {3, 1, 7}
    iex> Calendar.ISO.day_of_week(2016, 11, 3, :monday)
    {4, 1, 7}
    iex> Calendar.ISO.day_of_week(2016, 11, 4, :monday)
    {5, 1, 7}
    iex> Calendar.ISO.day_of_week(2016, 11, 5, :monday)
    {6, 1, 7}
    iex> Calendar.ISO.day_of_week(2016, 11, 6, :monday)
    {7, 1, 7}
    iex> Calendar.ISO.day_of_week(-99, 1, 31, :monday)
    {4, 1, 7}

    iex> Calendar.ISO.day_of_week(2016, 10, 31, :sunday)
    {2, 1, 7}
    iex> Calendar.ISO.day_of_week(2016, 11, 1, :sunday)
    {3, 1, 7}
    iex> Calendar.ISO.day_of_week(2016, 11, 2, :sunday)
    {4, 1, 7}
    iex> Calendar.ISO.day_of_week(2016, 11, 3, :sunday)
    {5, 1, 7}
    iex> Calendar.ISO.day_of_week(2016, 11, 4, :sunday)
    {6, 1, 7}
    iex> Calendar.ISO.day_of_week(2016, 11, 5, :sunday)
    {7, 1, 7}
    iex> Calendar.ISO.day_of_week(2016, 11, 6, :sunday)
    {1, 1, 7}
    iex> Calendar.ISO.day_of_week(-99, 1, 31, :sunday)
    {5, 1, 7}

    iex> Calendar.ISO.day_of_week(2016, 10, 31, :saturday)
    {3, 1, 7}

Link to this function

# day_of_year(year, month, day)

View Source (since 1.8.0)

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

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

It is an integer from 1 to 366.

## Examples

    iex> Calendar.ISO.day_of_year(2016, 1, 31)
    31
    iex> Calendar.ISO.day_of_year(-99, 2, 1)
    32
    iex> Calendar.ISO.day_of_year(2018, 2, 28)
    59

Link to this function

# day_rollover_relative_to_midnight_utc()

View Source (since 1.5.0)

    @spec day_rollover_relative_to_midnight_utc() :: {0, 1}

See `Calendar.day_rollover_relative_to_midnight_utc/0` for documentation.

Link to this function

# days_in_month(year, month)

View Source (since 1.4.0)

    @spec days_in_month(year(), month()) :: 28..31

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

## Examples

    iex> Calendar.ISO.days_in_month(1900, 1)
    31
    iex> Calendar.ISO.days_in_month(1900, 2)
    28
    iex> Calendar.ISO.days_in_month(2000, 2)
    29
    iex> Calendar.ISO.days_in_month(2001, 2)
    28
    iex> Calendar.ISO.days_in_month(2004, 2)
    29
    iex> Calendar.ISO.days_in_month(2004, 4)
    30
    iex> Calendar.ISO.days_in_month(-1, 5)
    31

Link to this function

# iso_days_to_beginning_of_day(arg)

View Source (since 1.15.0)

    @spec iso_days_to_beginning_of_day(Calendar.iso_days()) :: Calendar.iso_days()

Converts the `Calendar.iso_days/0` to the first moment of the day.

## Examples

    iex> Calendar.ISO.iso_days_to_beginning_of_day({0, {0, 86400000000}})
    {0, {0, 86400000000}}
    iex> Calendar.ISO.iso_days_to_beginning_of_day({730485, {43200000000, 86400000000}})
    {730485, {0, 86400000000}}
    iex> Calendar.ISO.iso_days_to_beginning_of_day({730485, {46800000000, 86400000000}})
    {730485, {0, 86400000000}}

Link to this function

# iso_days_to_end_of_day(arg)

View Source (since 1.15.0)

    @spec iso_days_to_end_of_day(Calendar.iso_days()) :: Calendar.iso_days()

Converts the `Calendar.iso_days/0` to the last moment of the day.

## Examples

    iex> Calendar.ISO.iso_days_to_end_of_day({0, {0, 86400000000}})
    {0, {86399999999, 86400000000}}
    iex> Calendar.ISO.iso_days_to_end_of_day({730485, {43200000000, 86400000000}})
    {730485, {86399999999, 86400000000}}
    iex> Calendar.ISO.iso_days_to_end_of_day({730485, {46800000000, 86400000000}})
    {730485, {86399999999, 86400000000}}

Link to this function

# leap_year?(year)

View Source (since 1.3.0)

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

Returns if the given year is a leap year.

## Examples

    iex> Calendar.ISO.leap_year?(2000)
    true
    iex> Calendar.ISO.leap_year?(2001)
    false
    iex> Calendar.ISO.leap_year?(2004)
    true
    iex> Calendar.ISO.leap_year?(1900)
    false
    iex> Calendar.ISO.leap_year?(-4)
    true

Link to this function

# months_in_year(year)

View Source (since 1.7.0)

    @spec months_in_year(year()) :: 12

Returns how many months there are in the given year.

## Example

    iex> Calendar.ISO.months_in_year(2004)
    12

Link to this function

# naive_datetime_from_iso_days(arg)

View Source (since 1.5.0)

    @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 `Calendar.iso_days/0` format to the datetime format specified by this calendar.

## Examples

    iex> Calendar.ISO.naive_datetime_from_iso_days({0, {0, 86400}})
    {0, 1, 1, 0, 0, 0, {0, 6}}
    iex> Calendar.ISO.naive_datetime_from_iso_days({730_485, {0, 86400}})
    {2000, 1, 1, 0, 0, 0, {0, 6}}
    iex> Calendar.ISO.naive_datetime_from_iso_days({730_485, {43200, 86400}})
    {2000, 1, 1, 12, 0, 0, {0, 6}}
    iex> Calendar.ISO.naive_datetime_from_iso_days({-365, {0, 86400000000}})
    {-1, 1, 1, 0, 0, 0, {0, 6}}

Link to this function

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

View Source (since 1.5.0)

    @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 `Calendar.iso_days/0` format of the specified date.

## Examples

    iex> Calendar.ISO.naive_datetime_to_iso_days(0, 1, 1, 0, 0, 0, {0, 6})
    {0, {0, 86400000000}}
    iex> Calendar.ISO.naive_datetime_to_iso_days(2000, 1, 1, 12, 0, 0, {0, 6})
    {730485, {43200000000, 86400000000}}
    iex> Calendar.ISO.naive_datetime_to_iso_days(2000, 1, 1, 13, 0, 0, {0, 6})
    {730485, {46800000000, 86400000000}}
    iex> Calendar.ISO.naive_datetime_to_iso_days(-1, 1, 1, 0, 0, 0, {0, 6})
    {-365, {0, 86400000000}}

Link to this function

# naive_datetime_to_string(year, month, day, hour, minute, second, microsecond, format \\ :extended)

View Source (since 1.4.0)

    @spec naive_datetime_to_string(
      year(),
      month(),
      day(),
      Calendar.hour(),
      Calendar.minute(),
      Calendar.second(),
      Calendar.microsecond(),
      :basic | :extended
    ) :: String.t()

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

By default, returns datetimes formatted in the "extended" format, for human readability. It also supports the "basic" format by passing the `:basic` option.

## Examples

    iex> Calendar.ISO.naive_datetime_to_string(2015, 2, 28, 1, 2, 3, {4, 6})
    "2015-02-28 01:02:03.000004"
    iex> Calendar.ISO.naive_datetime_to_string(2017, 8, 1, 1, 2, 3, {4, 5})
    "2017-08-01 01:02:03.00000"

    iex> Calendar.ISO.naive_datetime_to_string(2015, 2, 28, 1, 2, 3, {4, 6}, :basic)
    "20150228 010203.000004"

Link to this function

# parse_date(string)

View Source (since 1.10.0)

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

Parses a date `string` in the `:extended` format.

For more information on supported strings, see how this module implements ISO 8601.

## Examples

    iex> Calendar.ISO.parse_date("2015-01-23")
    {:ok, {2015, 1, 23}}

    iex> Calendar.ISO.parse_date("2015:01:23")
    {:error, :invalid_format}
    iex> Calendar.ISO.parse_date("2015-01-32")
    {:error, :invalid_date}

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# parse_date(string, format)

View Source (since 1.12.0)

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

Parses a date `string` according to a given `format`.

The `format` can either be `:basic` or `:extended`.

For more information on supported strings, see how this module implements ISO 8601.

## Examples

    iex> Calendar.ISO.parse_date("20150123", :basic)
    {:ok, {2015, 1, 23}}
    iex> Calendar.ISO.parse_date("20150123", :extended)
    {:error, :invalid_format}

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# parse_naive_datetime(string)

View Source (since 1.10.0)

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

Parses a naive datetime `string` in the `:extended` format.

For more information on supported strings, see how this module implements ISO 8601.

## Examples

    iex> Calendar.ISO.parse_naive_datetime("2015-01-23 23:50:07")
    {:ok, {2015, 1, 23, 23, 50, 7, {0, 0}}}
    iex> Calendar.ISO.parse_naive_datetime("2015-01-23 23:50:07Z")
    {:ok, {2015, 1, 23, 23, 50, 7, {0, 0}}}
    iex> Calendar.ISO.parse_naive_datetime("2015-01-23 23:50:07-02:30")
    {:ok, {2015, 1, 23, 23, 50, 7, {0, 0}}}

    iex> Calendar.ISO.parse_naive_datetime("2015-01-23 23:50:07.0")
    {:ok, {2015, 1, 23, 23, 50, 7, {0, 1}}}
    iex> Calendar.ISO.parse_naive_datetime("2015-01-23 23:50:07,0123456")
    {:ok, {2015, 1, 23, 23, 50, 7, {12345, 6}}}

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# parse_naive_datetime(string, format)

View Source (since 1.12.0)

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

Parses a naive datetime `string` according to a given `format`.

The `format` can either be `:basic` or `:extended`.

For more information on supported strings, see how this module implements ISO 8601.

## Examples

    iex> Calendar.ISO.parse_naive_datetime("20150123 235007", :basic)
    {:ok, {2015, 1, 23, 23, 50, 7, {0, 0}}}
    iex> Calendar.ISO.parse_naive_datetime("20150123 235007", :extended)
    {:error, :invalid_format}

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# parse_time(string)

View Source (since 1.10.0)

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

Parses a time `string` in the `:extended` format.

For more information on supported strings, see how this module implements ISO 8601.

## Examples

    iex> Calendar.ISO.parse_time("23:50:07")
    {:ok, {23, 50, 7, {0, 0}}}

    iex> Calendar.ISO.parse_time("23:50:07Z")
    {:ok, {23, 50, 7, {0, 0}}}
    iex> Calendar.ISO.parse_time("T23:50:07Z")
    {:ok, {23, 50, 7, {0, 0}}}

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# parse_time(string, format)

View Source (since 1.12.0)

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

Parses a time `string` according to a given `format`.

The `format` can either be `:basic` or `:extended`.

For more information on supported strings, see how this module implements ISO 8601.

## Examples

    iex> Calendar.ISO.parse_time("235007", :basic)
    {:ok, {23, 50, 7, {0, 0}}}
    iex> Calendar.ISO.parse_time("235007", :extended)
    {:error, :invalid_format}

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# parse_utc_datetime(string)

View Source (since 1.10.0)

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

Parses a UTC datetime `string` in the `:extended` format.

For more information on supported strings, see how this module implements ISO 8601.

## Examples

    iex> Calendar.ISO.parse_utc_datetime("2015-01-23 23:50:07Z")
    {:ok, {2015, 1, 23, 23, 50, 7, {0, 0}}, 0}

    iex> Calendar.ISO.parse_utc_datetime("2015-01-23 23:50:07+02:30")
    {:ok, {2015, 1, 23, 21, 20, 7, {0, 0}}, 9000}

    iex> Calendar.ISO.parse_utc_datetime("2015-01-23 23:50:07")
    {:error, :missing_offset}

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# parse_utc_datetime(string, format)

View Source (since 1.12.0)

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

Parses a UTC datetime `string` according to a given `format`.

The `format` can either be `:basic` or `:extended`.

For more information on supported strings, see how this module implements ISO 8601.

## Examples

    iex> Calendar.ISO.parse_utc_datetime("20150123 235007Z", :basic)
    {:ok, {2015, 1, 23, 23, 50, 7, {0, 0}}, 0}
    iex> Calendar.ISO.parse_utc_datetime("20150123 235007Z", :extended)
    {:error, :invalid_format}

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# quarter_of_year(year, month, day)

View Source (since 1.8.0)

    @spec quarter_of_year(year(), month(), day()) :: quarter_of_year()

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

It is an integer from 1 to 4.

## Examples

    iex> Calendar.ISO.quarter_of_year(2016, 1, 31)
    1
    iex> Calendar.ISO.quarter_of_year(2016, 4, 3)
    2
    iex> Calendar.ISO.quarter_of_year(-99, 9, 31)
    3
    iex> Calendar.ISO.quarter_of_year(2018, 12, 28)
    4

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# time_from_day_fraction(arg)

View Source (since 1.5.0)

    @spec time_from_day_fraction(Calendar.day_fraction()) ::
      {hour(), minute(), second(), microsecond()}

Converts a day fraction to this Calendar's representation of time.

## Examples

    iex> Calendar.ISO.time_from_day_fraction({1, 2})
    {12, 0, 0, {0, 6}}
    iex> Calendar.ISO.time_from_day_fraction({13, 24})
    {13, 0, 0, {0, 6}}

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# time_to_day_fraction(hour, minute, second, arg)

View Source (since 1.5.0)

    @spec time_to_day_fraction(
      Calendar.hour(),
      Calendar.minute(),
      Calendar.second(),
      Calendar.microsecond()
    ) :: Calendar.day_fraction()

Returns the normalized day fraction of the specified time.

## Examples

    iex> Calendar.ISO.time_to_day_fraction(0, 0, 0, {0, 6})
    {0, 86400000000}
    iex> Calendar.ISO.time_to_day_fraction(12, 34, 56, {123, 6})
    {45296000123, 86400000000}

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# time_to_string(hour, minute, second, microsecond, format \\ :extended)

View Source (since 1.5.0)

    @spec time_to_string(
      Calendar.hour(),
      Calendar.minute(),
      Calendar.second(),
      Calendar.microsecond(),
      :basic | :extended
    ) :: String.t()

Converts the given time into a string.

By default, returns times formatted in the "extended" format, for human readability. It also supports the "basic" format by passing the `:basic` option.

## Examples

    iex> Calendar.ISO.time_to_string(2, 2, 2, {2, 6})
    "02:02:02.000002"
    iex> Calendar.ISO.time_to_string(2, 2, 2, {2, 2})
    "02:02:02.00"
    iex> Calendar.ISO.time_to_string(2, 2, 2, {2, 0})
    "02:02:02"

    iex> Calendar.ISO.time_to_string(2, 2, 2, {2, 6}, :basic)
    "020202.000002"
    iex> Calendar.ISO.time_to_string(2, 2, 2, {2, 6}, :extended)
    "02:02:02.000002"

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# time_unit_to_precision(int)

View Source (since 1.15.0)

    @spec time_unit_to_precision(System.time_unit()) :: 0..6

Converts a `System.time_unit/0` to precision.

Integer-based time units always get maximum precision.

## Examples

    iex> Calendar.ISO.time_unit_to_precision(:nanosecond)
    6

    iex> Calendar.ISO.time_unit_to_precision(:second)
    0

    iex> Calendar.ISO.time_unit_to_precision(1)
    6

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# valid_date?(year, month, day)

View Source (since 1.5.0)

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

Determines if the date given is valid according to the proleptic Gregorian calendar.

## Examples

    iex> Calendar.ISO.valid_date?(2015, 2, 28)
    true
    iex> Calendar.ISO.valid_date?(2015, 2, 30)
    false
    iex> Calendar.ISO.valid_date?(-1, 12, 31)
    true
    iex> Calendar.ISO.valid_date?(-1, 12, 32)
    false

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# valid_time?(hour, minute, second, microsecond)

View Source (since 1.5.0)

    @spec valid_time?(
      Calendar.hour(),
      Calendar.minute(),
      Calendar.second(),
      Calendar.microsecond()
    ) ::
      boolean()

Determines if the date given is valid according to the proleptic Gregorian calendar.

Leap seconds are not supported by the built-in Calendar.ISO.

## Examples

    iex> Calendar.ISO.valid_time?(10, 50, 25, {3006, 6})
    true
    iex> Calendar.ISO.valid_time?(23, 59, 60, {0, 0})
    false
    iex> Calendar.ISO.valid_time?(24, 0, 0, {0, 0})
    false

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# year_of_era(year)

View Source (since 1.8.0)

    @spec year_of_era(year()) :: {1..10000, era()}

Calculates the year and era from the given `year`.

The ISO calendar has two eras: the "current era" (CE) which starts in year `1` and is defined as era `1`. And "before the current era" (BCE) for those years less than `1`, defined as era `0`.

## Examples

    iex> Calendar.ISO.year_of_era(1)
    {1, 1}
    iex> Calendar.ISO.year_of_era(2018)
    {2018, 1}
    iex> Calendar.ISO.year_of_era(0)
    {1, 0}
    iex> Calendar.ISO.year_of_era(-1)
    {2, 0}

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# year_of_era(year, month, day)

View Source (since 1.13.0)

    @spec year_of_era(year(), month(), day()) :: {1..10000, era()}

Calendar callback to compute the year and era from the given `year`, `month` and `day`.

In the ISO calendar, the new year coincides with the new era, so the `month` and `day` arguments are discarded. If you only have the year available, you can `year_of_era/1` instead.

## Examples

    iex> Calendar.ISO.year_of_era(1, 1, 1)
    {1, 1}
    iex> Calendar.ISO.year_of_era(2018, 12, 1)
    {2018, 1}
    iex> Calendar.ISO.year_of_era(0, 1, 1)
    {1, 0}
    iex> Calendar.ISO.year_of_era(-1, 12, 1)
    {2, 0}