DateTime

A datetime implementation with a time zone.

This datetime can be seen as an ephemeral snapshot of a datetime at a given timezone. For such purposes, it also includes both UTC and Standard offsets, as well as the zone abbreviation field used exclusively for formatting purposes.

Developers should avoid creating the DateTime struct directly and instead rely on the functions provided by this module as well as the ones in 3rd party calendar libraries.

Where are my functions?

You will notice this module only contains conversion functions as well as functions that work on UTC. This is because a proper DateTime implementation requires a TimeZone database which currently is not provided as part of Elixir.

Such may be addressed in upcoming versions, meanwhile, use 3rd party packages to provide DateTime building and similar functionality with time zone backing.

Summary

Types

t()

Functions

from_unix(integer, unit \\ :seconds)

Converts the given Unix time to DateTime

from_unix!(integer, unit \\ :seconds)

Converts the given Unix time to DateTime

precision_for_unit(unit)
to_date(date_time)

Converts a DateTime into a Date

to_iso8601(dt)

Converts the given date time to ISO8601

to_naive(date_time)

Converts a DateTime into a NaiveDateTime

to_string(dt)

Converts the given date time to a string according to its calendar

to_time(date_time)

Converts a DateTime into Time

to_unix(datetime, unit \\ :seconds)

Converts the given DateTime to Unix time

utc_now()

Returns the current datetime in UTC

Types

t() 

t() :: %DateTime{calendar: Calendar.calendar, day: Calendar.day, hour: Calendar.hour, microsecond: Calendar.microsecond, minute: Calendar.minute, month: Calendar.month, second: Calendar.second, std_offset: Calendar.std_offset, time_zone: Calendar.time_zone, utc_offset: Calendar.utc_offset, year: Calendar.year, zone_abbr: Calendar.zone_abbr}

Functions

from_unix(integer, unit \\ :seconds) 

from_unix(integer, :native | System.time_unit) :: {:ok, DateTime.t}

Converts the given Unix time to DateTime.

The integer can be given in different unit according to System.convert_time_unit/3 and it will be converted to microseconds internally.

Unix times are always in UTC and therefore the DateTime will be returned in UTC.

Examples 

iex> DateTime.from_unix(1464096368)
{:ok, %DateTime{calendar: Calendar.ISO, day: 24, hour: 13, microsecond: {0, 0}, minute: 26,
                month: 5, second: 8, std_offset: 0, time_zone: "Etc/UTC", utc_offset: 0,
                year: 2016, zone_abbr: "UTC"}}

iex> DateTime.from_unix(1432560368868569, :microseconds)
{:ok, %DateTime{calendar: Calendar.ISO, day: 25, hour: 13, microsecond: {868569, 6}, minute: 26,
                month: 5, second: 8, std_offset: 0, time_zone: "Etc/UTC", utc_offset: 0,
                year: 2015, zone_abbr: "UTC"}}

The unit can also be an integer as in System.time_unit:

iex> DateTime.from_unix(1432560368868569, 1024)
{:ok, %DateTime{calendar: Calendar.ISO, day: 23, hour: 22, microsecond: {211914, 3}, minute: 53,
                month: 1, second: 43, std_offset: 0, time_zone: "Etc/UTC", utc_offset: 0,
                year: 46302, zone_abbr: "UTC"}}

Negative Unix times are supported, up to -62167219200 seconds, which is equivalent to “0000-01-01T00:00:00Z” or 0 gregorian seconds.

iex> DateTime.from_unix(-12345678910)
{:ok, %DateTime{calendar: Calendar.ISO, day: 13, hour: 4, microsecond: {0, 0}, minute: 44, 
                month: 10, second: 50, std_offset: 0, time_zone: "Etc/UTC", utc_offset: 0, 
                year: 1578, zone_abbr: "UTC"}}

When a Unix time before that moment is passed to from_unix/2, :error will be returned.

from_unix!(integer, unit \\ :seconds) 

from_unix!(non_neg_integer, :native | System.time_unit) :: DateTime.t

Converts the given Unix time to DateTime.

The integer can be given in different unit according to System.convert_time_unit/3 and it will be converted to microseconds internally.

Unix times are always in UTC and therefore the DateTime will be returned in UTC.

Examples 

iex> DateTime.from_unix!(1464096368)
%DateTime{calendar: Calendar.ISO, day: 24, hour: 13, microsecond: {0, 0}, minute: 26,
          month: 5, second: 8, std_offset: 0, time_zone: "Etc/UTC", utc_offset: 0,
          year: 2016, zone_abbr: "UTC"}

iex> DateTime.from_unix!(1432560368868569, :microseconds)
%DateTime{calendar: Calendar.ISO, day: 25, hour: 13, microsecond: {868569, 6}, minute: 26,
          month: 5, second: 8, std_offset: 0, time_zone: "Etc/UTC", utc_offset: 0,
          year: 2015, zone_abbr: "UTC"}

Negative Unix times are supported, up to -62167219200 seconds, which is equivalent to “0000-01-01T00:00:00Z” or 0 gregorian seconds.

iex> DateTime.from_unix(-12345678910)
{:ok, %DateTime{calendar: Calendar.ISO, day: 13, hour: 4, microsecond: {0, 0}, minute: 44, 
                month: 10, second: 50, std_offset: 0, time_zone: "Etc/UTC", utc_offset: 0, 
                year: 1578, zone_abbr: "UTC"}}

When a Unix time before that moment is passed to from_unix!/2, an ArgumentError will be raised.

precision_for_unit(unit)

to_date(date_time)

Converts a DateTime into a Date.

Because Date does not hold time nor timezone information, data will be lost during the conversion.

Examples 

iex> dt = %DateTime{year: 2000, month: 2, day: 29, zone_abbr: "CET",
...>                hour: 23, minute: 0, second: 7, microsecond: {0, 0},
...>                utc_offset: 3600, std_offset: 0, time_zone: "Europe/Warsaw"}
iex> DateTime.to_date(dt)
~D[2000-02-29]

to_iso8601(dt) 

to_iso8601(DateTime.t) :: String.t

Converts the given date time to ISO8601.

Only supports converting date times which are in the ISO calendar, attempting to convert date times from other calendars will raise.

WARNING: the ISO8601 does not contain the time zone nor its abbreviation, which means information is lost when converting to such format. This is also why this module does not provide a from_iso8601/1 function, as it is impossible to build a proper DateTime from only the information in the ISO8601 string.

Examples

iex> dt = %DateTime{year: 2000, month: 2, day: 29, zone_abbr: "CET",
...>                hour: 23, minute: 0, second: 7, microsecond: {0, 0},
...>                utc_offset: 3600, std_offset: 0, time_zone: "Europe/Warsaw"}
iex> DateTime.to_iso8601(dt)
"2000-02-29T23:00:07+01:00"

iex> dt = %DateTime{year: 2000, month: 2, day: 29, zone_abbr: "UTC",
...>                hour: 23, minute: 0, second: 7, microsecond: {0, 0},
...>                utc_offset: 0, std_offset: 0, time_zone: "Etc/UTC"}
iex> DateTime.to_iso8601(dt)
"2000-02-29T23:00:07Z"

iex> dt = %DateTime{year: 2000, month: 2, day: 29, zone_abbr: "AMT",
...>                hour: 23, minute: 0, second: 7, microsecond: {0, 0},
...>                utc_offset: -14400, std_offset: 0, time_zone: "America/Manaus"}
iex> DateTime.to_iso8601(dt)
"2000-02-29T23:00:07-04:00"

to_naive(date_time)

Converts a DateTime into a NaiveDateTime.

Because NaiveDateTime does not hold timezone information, any timezone related data will be lost during the conversion.

Examples 

iex> dt = %DateTime{year: 2000, month: 2, day: 29, zone_abbr: "CET",
...>                hour: 23, minute: 0, second: 7, microsecond: {0, 1},
...>                utc_offset: 3600, std_offset: 0, time_zone: "Europe/Warsaw"}
iex> DateTime.to_naive(dt)
~N[2000-02-29 23:00:07.0]

to_string(dt) 

to_string(DateTime.t) :: String.t

Converts the given date time to a string according to its calendar.

Examples

iex> dt = %DateTime{year: 2000, month: 2, day: 29, zone_abbr: "CET",
...>                hour: 23, minute: 0, second: 7, microsecond: {0, 0},
...>                utc_offset: 3600, std_offset: 0, time_zone: "Europe/Warsaw"}
iex> DateTime.to_string(dt)
"2000-02-29 23:00:07+01:00 CET Europe/Warsaw"

iex> dt = %DateTime{year: 2000, month: 2, day: 29, zone_abbr: "UTC",
...>                hour: 23, minute: 0, second: 7, microsecond: {0, 0},
...>                utc_offset: 0, std_offset: 0, time_zone: "Etc/UTC"}
iex> DateTime.to_string(dt)
"2000-02-29 23:00:07Z"

iex> dt = %DateTime{year: 2000, month: 2, day: 29, zone_abbr: "AMT",
...>                hour: 23, minute: 0, second: 7, microsecond: {0, 0},
...>                utc_offset: -14400, std_offset: 0, time_zone: "America/Manaus"}
iex> DateTime.to_string(dt)
"2000-02-29 23:00:07-04:00 AMT America/Manaus"

to_time(date_time)

Converts a DateTime into Time.

Because Time does not hold date nor timezone information, data will be lost during the conversion.

Examples 

iex> dt = %DateTime{year: 2000, month: 2, day: 29, zone_abbr: "CET",
...>                hour: 23, minute: 0, second: 7, microsecond: {0, 1},
...>                utc_offset: 3600, std_offset: 0, time_zone: "Europe/Warsaw"}
iex> DateTime.to_time(dt)
~T[23:00:07.0]

to_unix(datetime, unit \\ :seconds) 

to_unix(DateTime.t, System.time_unit) :: non_neg_integer

Converts the given DateTime to Unix time.

The DateTime is expected to be using the ISO calendar with a year greater than or equal to 0.

It will return the integer with the given unit, according to System.convert_time_unit/3.

Examples 

iex> 1464096368 |> DateTime.from_unix!() |> DateTime.to_unix()
1464096368

iex> dt = %DateTime{calendar: Calendar.ISO, day: 20, hour: 18, microsecond: {273806, 6},
...>                minute: 58, month: 11, second: 19, time_zone: "America/Montevideo",
...>                utc_offset: -10800, std_offset: 3600, year: 2014, zone_abbr: "UYST"}
iex> DateTime.to_unix(dt)
1416517099

iex> flamel = %DateTime{calendar: Calendar.ISO, day: 22, hour: 8, microsecond: {527771, 6},
...>                minute: 2, month: 3, second: 25, std_offset: 0, time_zone: "Etc/UTC",
...>                utc_offset: 0, year: 1418, zone_abbr: "UTC"}
iex> DateTime.to_unix(flamel)
-17412508655

utc_now() 

utc_now() :: DateTime.t

Returns the current datetime in UTC.

Examples 

iex> datetime = DateTime.utc_now()
iex> datetime.time_zone
"Etc/UTC"

© 2012 Plataformatec
Licensed under the Apache License, Version 2.0.
https://hexdocs.pm/elixir/1.3.4/DateTime.html