View Source DateTime (Elixir v1.18.0)
A datetime implementation with a time zone.
This datetime can be seen as a snapshot of a date and time at a given time zone. For such purposes, it also includes both UTC and Standard offsets, as well as the zone abbreviation field used exclusively for formatting purposes. Note future datetimes are not necessarily guaranteed to exist, as time zones may change any time in the future due to geopolitical reasons. See the "Datetimes as snapshots" section for more information.
Remember, comparisons in Elixir using ==/2, >/2, </2 and friends
are structural and based on the DateTime struct fields. For proper
comparison between datetimes, use the compare/2 function. The
existence of the compare/2 function in this module also allows
using Enum.min/2 and Enum.max/2 functions to get the minimum and
maximum datetime of an Enum. For example:
iex> Enum.min([~U[2022-01-12 00:01:00.00Z], ~U[2021-01-12 00:01:00.00Z]], DateTime)
~U[2021-01-12 00:01:00.00Z]Developers should avoid creating the DateTime struct directly
and instead rely on the functions provided by this module as
well as the ones in third-party calendar libraries.
Time zone database
Many functions in this module require a time zone database. A time zone database is a record of the UTC offsets that its locales have used at various times in the past, are using, and are expected to use in the future. Because those plans can change, it needs to be periodically updated.
By default, DateTime 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 can also be configured. Here are some available options and libraries:
time_zone_infotztzdatazoneinfo- recommended for embedded devices
To use one of them, first make sure it is added as a dependency in mix.exs.
It can then be configured either via configuration:
config :elixir, :time_zone_database, Tz.TimeZoneDatabaseor by calling Calendar.put_time_zone_database/1:
Calendar.put_time_zone_database(Tz.TimeZoneDatabase)See the proper names in the library installation instructions.
Datetimes as snapshots
In the first section, we described datetimes as a "snapshot of a date and time at a given time zone". To understand precisely what we mean, let's see an example.
Imagine someone in Poland who wants to schedule a meeting with someone in Brazil in the next year. The meeting will happen at 2:30 AM in the Polish time zone. At what time will the meeting happen in Brazil?
You can consult the time zone database today, one year before, using the API in this module and it will give you an answer that is valid right now. However, this answer may not be valid in the future. Why? Because both Brazil and Poland may change their timezone rules, ultimately affecting the result. For example, a country may choose to enter or abandon "Daylight Saving Time", which is a process where we adjust the clock one hour forward or one hour back once per year. Whenever the rules change, the exact instant that 2:30 AM in Polish time will be in Brazil may change.
In other words, whenever working with future DateTimes, there is no guarantee the results you get will always be correct, until the event actually happens. Therefore, when you ask for a future time, the answers you get are a snapshot that reflects the current state of the time zone rules. For datetimes in the past, this is not a problem, because time zone rules do not change for past events.
To make matters worse, it may be that 2:30 AM in Polish time does not actually even exist or it is ambiguous. If a certain time zone observes "Daylight Saving Time", they will move their clock forward once a year. When this happens, there is a whole hour that does not exist. Then, when they move the clock back, there is a certain hour that will happen twice. So if you want to schedule a meeting when this shift back happens, you would need to explicitly say which occurrence of 2:30 AM you mean: the one in "Summer Time", which occurs before the shift, or the one in "Standard Time", which occurs after it. Applications that are date and time sensitive need to take these scenarios into account and correctly communicate them to users.
The good news is: Elixir contains all of the building blocks
necessary to tackle those problems. The default timezone database
used by Elixir, Calendar.UTCOnlyTimeZoneDatabase, only works
with UTC, which does not observe those issues. Once you bring
a proper time zone database, the functions in this module will
query the database and return the relevant information. For
example, look at how DateTime.new/4 returns different results
based on the scenarios described in this section.
Converting between timezones
Bearing in mind the cautions above, and assuming you've brought in a full timezone database, here are some examples of common shifts between time zones.
# Local time to UTC
new_york = DateTime.from_naive!(~N[2023-06-26T09:30:00], "America/New_York")
#=> #DateTime<2023-06-26 09:30:00-04:00 EDT America/New_York>
utc = DateTime.shift_zone!(new_york, "Etc/UTC")
#=> ~U[2023-06-26 13:30:00Z]
# UTC to local time
DateTime.shift_zone!(utc, "Europe/Paris")
#=> #DateTime<2023-06-26 15:30:00+02:00 CEST Europe/Paris>Summary
Functions
Adds a specified amount of time to a DateTime.
Returns true if the first datetime is strictly later than the second.
Returns true if the first datetime is strictly earlier than the second.
Compares two datetime structs.
Converts a given datetime from one calendar to another.
Converts a given datetime from one calendar to another.
Subtracts datetime2 from datetime1.
Converts a number of gregorian seconds to a DateTime struct.
Parses the extended "Date and time of day" format described by ISO 8601:2019.
Converts from ISO8601 specifying both a calendar and a mode.
Converts the given NaiveDateTime to DateTime.
Converts the given NaiveDateTime to DateTime.
Converts the given Unix time to DateTime.
Converts the given Unix time to DateTime.
Builds a datetime from date and time structs.
Builds a datetime from date and time structs, raising on errors.
Returns the current datetime in the provided time zone.
Returns the current datetime in the provided time zone or raises on errors
Shifts given datetime by duration according to its calendar.
Changes the time zone of a DateTime.
Changes the time zone of a DateTime or raises on errors.
Converts a DateTime struct to a number of gregorian seconds and microseconds.
Converts the given datetime to ISO 8601:2019 format.
Converts the given datetime into a NaiveDateTime.
Converts the given datetime to a string according to its calendar.
Converts the given datetime to Unix time.
Returns the given datetime with the microsecond field truncated to the given
precision (:microsecond, :millisecond or :second).
Returns the current datetime in UTC.
Returns the current datetime in UTC, supporting a specific calendar and precision.
Types
@type 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
add(datetime, amount_to_add, unit \\ :second, time_zone_database \\ Calendar.get_time_zone_database())
(since 1.8.0)@spec add( Calendar.datetime(), integer(), :day | :hour | :minute | System.time_unit(), Calendar.time_zone_database() ) :: t()
Adds a specified amount of time to a DateTime.
Accepts an amount_to_add in any unit. unit can be :day,
:hour, :minute, :second or any subsecond precision from
System.time_unit/0. It defaults to :second. Negative values
will move backwards in time.
This function always considers the unit to be computed according
to the Calendar.ISO.
This function relies on a contiguous representation of time, ignoring the wall time and timezone changes. For example, if you add one day when there are summer time/daylight saving time changes, it will also change the time forward or backward by one hour, so the elapsed time is precisely 24 hours. Similarly, adding just a few seconds to a datetime just before "spring forward" can cause wall time to increase by more than an hour.
While this means this function is precise in terms of elapsed time, its result may be misleading in certain use cases. For example, if a user requests a meeting to happen every day at 15:00 and you use this function to compute all future meetings by adding day after day, this function may change the meeting time to 14:00 or 16:00 if there are changes to the current timezone. Computing of recurring datetimes is not currently supported in Elixir's standard library but it is available by third-party libraries.
Examples
iex> dt = DateTime.from_naive!(~N[2018-11-15 10:00:00], "Europe/Copenhagen", FakeTimeZoneDatabase)
iex> dt |> DateTime.add(3600, :second, FakeTimeZoneDatabase)
#DateTime<2018-11-15 11:00:00+01:00 CET Europe/Copenhagen>
iex> DateTime.add(~U[2018-11-15 10:00:00Z], 3600, :second)
~U[2018-11-15 11:00:00Z]When adding 3 seconds just before "spring forward" we go from 1:59:59 to 3:00:02:
iex> dt = DateTime.from_naive!(~N[2019-03-31 01:59:59.123], "Europe/Copenhagen", FakeTimeZoneDatabase)
iex> dt |> DateTime.add(3, :second, FakeTimeZoneDatabase)
#DateTime<2019-03-31 03:00:02.123+02:00 CEST Europe/Copenhagen>When adding 1 day during "spring forward", the hour also changes:
iex> dt = DateTime.from_naive!(~N[2019-03-31 01:00:00], "Europe/Copenhagen", FakeTimeZoneDatabase)
iex> dt |> DateTime.add(1, :day, FakeTimeZoneDatabase)
#DateTime<2019-04-01 02:00:00+02:00 CEST Europe/Copenhagen>This operation merges the precision of the naive date time with the given unit:
iex> result = DateTime.add(~U[2014-10-02 00:29:10Z], 21, :millisecond)
~U[2014-10-02 00:29:10.021Z]
iex> result.microsecond
{21000, 3}To shift a datetime by a Duration and according to its underlying calendar, use DateTime.shift/3.
@spec after?(Calendar.datetime(), Calendar.datetime()) :: boolean()
Returns true if the first datetime is strictly later than the second.
Examples
iex> DateTime.after?(~U[2022-02-02 11:00:00Z], ~U[2021-01-01 11:00:00Z])
true
iex> DateTime.after?(~U[2021-01-01 11:00:00Z], ~U[2021-01-01 11:00:00Z])
false
iex> DateTime.after?(~U[2021-01-01 11:00:00Z], ~U[2022-02-02 11:00:00Z])
false@spec before?(Calendar.datetime(), Calendar.datetime()) :: boolean()
Returns true if the first datetime is strictly earlier than the second.
Examples
iex> DateTime.before?(~U[2021-01-01 11:00:00Z], ~U[2022-02-02 11:00:00Z])
true
iex> DateTime.before?(~U[2021-01-01 11:00:00Z], ~U[2021-01-01 11:00:00Z])
false
iex> DateTime.before?(~U[2022-02-02 11:00:00Z], ~U[2021-01-01 11:00:00Z])
false@spec compare(Calendar.datetime(), Calendar.datetime()) :: :lt | :eq | :gt
Compares two datetime structs.
Returns :gt if the first datetime is later than the second
and :lt for vice versa. If the two datetimes are equal
:eq is returned.
Note that both UTC and Standard offsets will be taken into account when comparison is done.
Examples
iex> dt1 = %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> dt2 = %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.compare(dt1, dt2)
:gt@spec convert(Calendar.datetime(), Calendar.calendar()) :: {:ok, t()} | {:error, :incompatible_calendars}
Converts a given datetime from one calendar to another.
If it is not possible to convert unambiguously between the calendars
(see Calendar.compatible_calendars?/2), an {:error, :incompatible_calendars} tuple
is returned.
Examples
Imagine someone implements Calendar.Holocene, a calendar based on the
Gregorian calendar that adds exactly 10,000 years to the current Gregorian
year:
iex> dt1 = %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.convert(dt1, Calendar.Holocene)
{:ok, %DateTime{calendar: Calendar.Holocene, day: 29, hour: 23,
microsecond: {0, 0}, minute: 0, month: 2, second: 7, std_offset: 0,
time_zone: "America/Manaus", utc_offset: -14400, year: 12000,
zone_abbr: "AMT"}}@spec convert!(Calendar.datetime(), Calendar.calendar()) :: t()
Converts a given datetime from one calendar to another.
If it is not possible to convert unambiguously between the calendars
(see Calendar.compatible_calendars?/2), an ArgumentError is raised.
Examples
Imagine someone implements Calendar.Holocene, a calendar based on the
Gregorian calendar that adds exactly 10,000 years to the current Gregorian
year:
iex> dt1 = %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.convert!(dt1, Calendar.Holocene)
%DateTime{calendar: Calendar.Holocene, day: 29, hour: 23,
microsecond: {0, 0}, minute: 0, month: 2, second: 7, std_offset: 0,
time_zone: "America/Manaus", utc_offset: -14400, year: 12000,
zone_abbr: "AMT"}@spec diff( Calendar.datetime(), Calendar.datetime(), :day | :hour | :minute | System.time_unit() ) :: integer()
Subtracts datetime2 from datetime1.
The answer can be returned in any :day, :hour, :minute, or any unit
available from System.time_unit/0. The unit is measured according to
Calendar.ISO and defaults to :second.
Fractional results are not supported and are truncated.
Examples
iex> DateTime.diff(~U[2024-01-15 10:00:10Z], ~U[2024-01-15 10:00:00Z])
10This function also considers timezone offsets:
iex> dt1 = %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> dt2 = %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.diff(dt1, dt2)
18000
iex> DateTime.diff(dt2, dt1)
-18000
iex> DateTime.diff(dt1, dt2, :hour)
5
iex> DateTime.diff(dt2, dt1, :hour)
-5@spec from_gregorian_seconds(integer(), Calendar.microsecond(), Calendar.calendar()) :: t()
Converts a number of gregorian seconds to a DateTime struct.
The returned DateTime will have UTC timezone, if you want other timezone, please use
DateTime.shift_zone/3.
Examples
iex> DateTime.from_gregorian_seconds(1)
~U[0000-01-01 00:00:01Z]
iex> DateTime.from_gregorian_seconds(63_755_511_991, {5000, 3})
~U[2020-05-01 00:26:31.005Z]
iex> DateTime.from_gregorian_seconds(-1)
~U[-0001-12-31 23:59:59Z]@spec from_iso8601(String.t(), Calendar.calendar() | :extended | :basic) :: {:ok, t(), Calendar.utc_offset()} | {:error, atom()}
Parses the extended "Date and time of day" format described by ISO 8601:2019.
Since ISO 8601 does not include the proper time zone, the given string will be converted to UTC and its offset in seconds will be returned as part of this function. Therefore offset information must be present in the string.
As specified in the standard, the separator "T" may be omitted if desired as there is no ambiguity within this function.
Note leap seconds are not supported by the built-in Calendar.ISO.
Examples
iex> {:ok, datetime, 0} = DateTime.from_iso8601("2015-01-23T23:50:07Z")
iex> datetime
~U[2015-01-23 23:50:07Z]
iex> {:ok, datetime, 9000} = DateTime.from_iso8601("2015-01-23T23:50:07.123+02:30")
iex> datetime
~U[2015-01-23 21:20:07.123Z]
iex> {:ok, datetime, 9000} = DateTime.from_iso8601("2015-01-23T23:50:07,123+02:30")
iex> datetime
~U[2015-01-23 21:20:07.123Z]
iex> {:ok, datetime, 0} = DateTime.from_iso8601("-2015-01-23T23:50:07Z")
iex> datetime
~U[-2015-01-23 23:50:07Z]
iex> {:ok, datetime, 9000} = DateTime.from_iso8601("-2015-01-23T23:50:07,123+02:30")
iex> datetime
~U[-2015-01-23 21:20:07.123Z]
iex> {:ok, datetime, 9000} = DateTime.from_iso8601("20150123T235007.123+0230", :basic)
iex> datetime
~U[2015-01-23 21:20:07.123Z]
iex> DateTime.from_iso8601("2015-01-23P23:50:07")
{:error, :invalid_format}
iex> DateTime.from_iso8601("2015-01-23T23:50:07")
{:error, :missing_offset}
iex> DateTime.from_iso8601("2015-01-23 23:50:61")
{:error, :invalid_time}
iex> DateTime.from_iso8601("2015-01-32 23:50:07")
{:error, :invalid_date}
iex> DateTime.from_iso8601("2015-01-23T23:50:07.123-00:00")
{:error, :invalid_format}@spec from_iso8601(String.t(), Calendar.calendar(), :extended | :basic) :: {:ok, t(), Calendar.utc_offset()} | {:error, atom()}
Converts from ISO8601 specifying both a calendar and a mode.
See from_iso8601/2 for more information.
Examples
iex> {:ok, datetime, 9000} = DateTime.from_iso8601("2015-01-23T23:50:07,123+02:30", Calendar.ISO, :extended)
iex> datetime
~U[2015-01-23 21:20:07.123Z]
iex> {:ok, datetime, 9000} = DateTime.from_iso8601("20150123T235007.123+0230", Calendar.ISO, :basic)
iex> datetime
~U[2015-01-23 21:20:07.123Z]from_naive(naive_datetime, time_zone, time_zone_database \\ Calendar.get_time_zone_database())
(since 1.4.0)@spec from_naive( Calendar.naive_datetime(), Calendar.time_zone(), Calendar.time_zone_database() ) :: {:ok, t()} | {:ambiguous, first_datetime :: t(), second_datetime :: t()} | {:gap, t(), t()} | {:error, :incompatible_calendars | :time_zone_not_found | :utc_only_time_zone_database}
Converts the given NaiveDateTime to DateTime.
It expects a time zone to put the NaiveDateTime in.
If the time zone is "Etc/UTC", it always succeeds. Otherwise,
the NaiveDateTime is checked against the time zone database
given as time_zone_database. See the "Time zone database"
section in the module documentation.
Examples
iex> DateTime.from_naive(~N[2016-05-24 13:26:08.003], "Etc/UTC")
{:ok, ~U[2016-05-24 13:26:08.003Z]}When the datetime is ambiguous - for instance during changing from summer to winter time - the two possible valid datetimes are returned in a tuple. The first datetime is also the one which comes first chronologically, while the second one comes last.
iex> {:ambiguous, first_dt, second_dt} = DateTime.from_naive(~N[2018-10-28 02:30:00], "Europe/Copenhagen", FakeTimeZoneDatabase)
iex> first_dt
#DateTime<2018-10-28 02:30:00+02:00 CEST Europe/Copenhagen>
iex> second_dt
#DateTime<2018-10-28 02:30:00+01:00 CET Europe/Copenhagen>When there is a gap in wall time - for instance in spring when the clocks are turned forward - the latest valid datetime just before the gap and the first valid datetime just after the gap.
iex> {:gap, just_before, just_after} = DateTime.from_naive(~N[2019-03-31 02:30:00], "Europe/Copenhagen", FakeTimeZoneDatabase)
iex> just_before
#DateTime<2019-03-31 01:59:59.999999+01:00 CET Europe/Copenhagen>
iex> just_after
#DateTime<2019-03-31 03:00:00+02:00 CEST Europe/Copenhagen>Most of the time there is one, and just one, valid datetime for a certain date and time in a certain time zone.
iex> {:ok, datetime} = DateTime.from_naive(~N[2018-07-28 12:30:00], "Europe/Copenhagen", FakeTimeZoneDatabase)
iex> datetime
#DateTime<2018-07-28 12:30:00+02:00 CEST Europe/Copenhagen>This function accepts any map or struct that contains at least the same fields as a NaiveDateTime
struct. The most common example of that is a DateTime. In this case the information about the time
zone of that DateTime is completely ignored. This is the same principle as passing a DateTime to
Date.to_iso8601/2. Date.to_iso8601/2 extracts only the date-specific fields (calendar, year,
month and day) of the given structure and ignores all others.
This way if you have a DateTime in one time zone, you can get the same wall time in another time zone.
For instance if you have 2018-08-24 10:00:00 in Copenhagen and want a DateTime for 2018-08-24 10:00:00
in UTC you can do:
iex> cph_datetime = DateTime.from_naive!(~N[2018-08-24 10:00:00], "Europe/Copenhagen", FakeTimeZoneDatabase)
iex> {:ok, utc_datetime} = DateTime.from_naive(cph_datetime, "Etc/UTC", FakeTimeZoneDatabase)
iex> utc_datetime
~U[2018-08-24 10:00:00Z]If instead you want a DateTime for the same point time in a different time zone see the
DateTime.shift_zone/3 function which would convert 2018-08-24 10:00:00 in Copenhagen
to 2018-08-24 08:00:00 in UTC.
from_naive!(naive_datetime, time_zone, time_zone_database \\ Calendar.get_time_zone_database())
(since 1.4.0)@spec from_naive!( NaiveDateTime.t(), Calendar.time_zone(), Calendar.time_zone_database() ) :: t()
Converts the given NaiveDateTime to DateTime.
It expects a time zone to put the NaiveDateTime in.
If the time zone is "Etc/UTC", it always succeeds. Otherwise,
the NaiveDateTime is checked against the time zone database
given as time_zone_database. See the "Time zone database"
section in the module documentation.
Examples
iex> DateTime.from_naive!(~N[2016-05-24 13:26:08.003], "Etc/UTC")
~U[2016-05-24 13:26:08.003Z]
iex> DateTime.from_naive!(~N[2018-05-24 13:26:08.003], "Europe/Copenhagen", FakeTimeZoneDatabase)
#DateTime<2018-05-24 13:26:08.003+02:00 CEST Europe/Copenhagen>@spec from_unix(integer(), :native | System.time_unit(), Calendar.calendar()) :: {:ok, t()} | {:error, atom()}
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. Up to
253402300799 seconds is supported.
Unix times are always in UTC and therefore the DateTime will be returned in UTC.
Examples
iex> {:ok, datetime} = DateTime.from_unix(1_464_096_368)
iex> datetime
~U[2016-05-24 13:26:08Z]
iex> {:ok, datetime} = DateTime.from_unix(1_432_560_368_868_569, :microsecond)
iex> datetime
~U[2015-05-25 13:26:08.868569Z]
iex> {:ok, datetime} = DateTime.from_unix(253_402_300_799)
iex> datetime
~U[9999-12-31 23:59:59Z]
iex> {:error, :invalid_unix_time} = DateTime.from_unix(253_402_300_800)The unit can also be an integer as in System.time_unit/0:
iex> {:ok, datetime} = DateTime.from_unix(143_256_036_886_856, 1024)
iex> datetime
~U[6403-03-17 07:05:22.320312Z]Negative Unix times are supported up to -377705116800 seconds:
iex> {:ok, datetime} = DateTime.from_unix(-377_705_116_800)
iex> datetime
~U[-9999-01-01 00:00:00Z]
iex> {:error, :invalid_unix_time} = DateTime.from_unix(-377_705_116_801)@spec from_unix!(integer(), :native | System.time_unit(), Calendar.calendar()) :: 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
# An easy way to get the Unix epoch is passing 0 to this function
iex> DateTime.from_unix!(0)
~U[1970-01-01 00:00:00Z]
iex> DateTime.from_unix!(1_464_096_368)
~U[2016-05-24 13:26:08Z]
iex> DateTime.from_unix!(1_432_560_368_868_569, :microsecond)
~U[2015-05-25 13:26:08.868569Z]
iex> DateTime.from_unix!(143_256_036_886_856, 1024)
~U[6403-03-17 07:05:22.320312Z]new(date, time, time_zone \\ "Etc/UTC", time_zone_database \\ Calendar.get_time_zone_database())
(since 1.11.0)@spec new(Date.t(), Time.t(), Calendar.time_zone(), Calendar.time_zone_database()) :: {:ok, t()} | {:ambiguous, first_datetime :: t(), second_datetime :: t()} | {:gap, t(), t()} | {:error, :incompatible_calendars | :time_zone_not_found | :utc_only_time_zone_database}
Builds a datetime from date and time structs.
It expects a time zone to put the DateTime in.
If the time zone is not passed it will default to "Etc/UTC",
which always succeeds. Otherwise, the DateTime is checked against the time zone database
given as time_zone_database. See the "Time zone database"
section in the module documentation.
Examples
iex> DateTime.new(~D[2016-05-24], ~T[13:26:08.003], "Etc/UTC")
{:ok, ~U[2016-05-24 13:26:08.003Z]}When the datetime is ambiguous - for instance during changing from summer to winter time - the two possible valid datetimes are returned in a tuple. The first datetime is also the one which comes first chronologically, while the second one comes last.
iex> {:ambiguous, first_dt, second_dt} = DateTime.new(~D[2018-10-28], ~T[02:30:00], "Europe/Copenhagen", FakeTimeZoneDatabase)
iex> first_dt
#DateTime<2018-10-28 02:30:00+02:00 CEST Europe/Copenhagen>
iex> second_dt
#DateTime<2018-10-28 02:30:00+01:00 CET Europe/Copenhagen>When there is a gap in wall time - for instance in spring when the clocks are turned forward - the latest valid datetime just before the gap and the first valid datetime just after the gap.
iex> {:gap, just_before, just_after} = DateTime.new(~D[2019-03-31], ~T[02:30:00], "Europe/Copenhagen", FakeTimeZoneDatabase)
iex> just_before
#DateTime<2019-03-31 01:59:59.999999+01:00 CET Europe/Copenhagen>
iex> just_after
#DateTime<2019-03-31 03:00:00+02:00 CEST Europe/Copenhagen>Most of the time there is one, and just one, valid datetime for a certain date and time in a certain time zone.
iex> {:ok, datetime} = DateTime.new(~D[2018-07-28], ~T[12:30:00], "Europe/Copenhagen", FakeTimeZoneDatabase)
iex> datetime
#DateTime<2018-07-28 12:30:00+02:00 CEST Europe/Copenhagen>new!(date, time, time_zone \\ "Etc/UTC", time_zone_database \\ Calendar.get_time_zone_database())
(since 1.11.0)@spec new!(Date.t(), Time.t(), Calendar.time_zone(), Calendar.time_zone_database()) :: t()
Builds a datetime from date and time structs, raising on errors.
It expects a time zone to put the DateTime in.
If the time zone is not passed it will default to "Etc/UTC",
which always succeeds. Otherwise, the DateTime is checked against the time zone database
given as time_zone_database. See the "Time zone database"
section in the module documentation.
Examples
iex> DateTime.new!(~D[2016-05-24], ~T[13:26:08.003], "Etc/UTC")
~U[2016-05-24 13:26:08.003Z]When the datetime is ambiguous - for instance during changing from summer to winter time - an error will be raised.
iex> DateTime.new!(~D[2018-10-28], ~T[02:30:00], "Europe/Copenhagen", FakeTimeZoneDatabase)
** (ArgumentError) cannot build datetime with ~D[2018-10-28] and ~T[02:30:00] because such instant is ambiguous in time zone Europe/Copenhagen as there is an overlap between #DateTime<2018-10-28 02:30:00+02:00 CEST Europe/Copenhagen> and #DateTime<2018-10-28 02:30:00+01:00 CET Europe/Copenhagen>When there is a gap in wall time - for instance in spring when the clocks are turned forward - an error will be raised.
iex> DateTime.new!(~D[2019-03-31], ~T[02:30:00], "Europe/Copenhagen", FakeTimeZoneDatabase)
** (ArgumentError) cannot build datetime with ~D[2019-03-31] and ~T[02:30:00] because such instant does not exist in time zone Europe/Copenhagen as there is a gap between #DateTime<2019-03-31 01:59:59.999999+01:00 CET Europe/Copenhagen> and #DateTime<2019-03-31 03:00:00+02:00 CEST Europe/Copenhagen>Most of the time there is one, and just one, valid datetime for a certain date and time in a certain time zone.
iex> datetime = DateTime.new!(~D[2018-07-28], ~T[12:30:00], "Europe/Copenhagen", FakeTimeZoneDatabase)
iex> datetime
#DateTime<2018-07-28 12:30:00+02:00 CEST Europe/Copenhagen>@spec now(Calendar.time_zone(), Calendar.time_zone_database()) :: {:ok, t()} | {:error, :time_zone_not_found | :utc_only_time_zone_database}
Returns the current datetime in the provided time zone.
By default, it uses the default time_zone returned by
Calendar.get_time_zone_database/0, which defaults to
Calendar.UTCOnlyTimeZoneDatabase which only handles "Etc/UTC" datetimes.
Other time zone databases can be passed as argument or set globally.
See the "Time zone database" section in the module docs.
Examples
iex> {:ok, datetime} = DateTime.now("Etc/UTC")
iex> datetime.time_zone
"Etc/UTC"
iex> DateTime.now("Europe/Copenhagen")
{:error, :utc_only_time_zone_database}
iex> DateTime.now("bad timezone", FakeTimeZoneDatabase)
{:error, :time_zone_not_found}@spec now!(Calendar.time_zone(), Calendar.time_zone_database()) :: t()
Returns the current datetime in the provided time zone or raises on errors
See now/2 for more information.
Examples
iex> datetime = DateTime.now!("Etc/UTC")
iex> datetime.time_zone
"Etc/UTC"
iex> DateTime.now!("Europe/Copenhagen")
** (ArgumentError) cannot get current datetime in "Europe/Copenhagen" time zone, reason: :utc_only_time_zone_database
iex> DateTime.now!("bad timezone", FakeTimeZoneDatabase)
** (ArgumentError) cannot get current datetime in "bad timezone" time zone, reason: :time_zone_not_found@spec shift(Calendar.datetime(), Duration.duration(), Calendar.time_zone_database()) :: t()
Shifts given datetime by duration according to its calendar.
Allowed units are: :year, :month, :week, :day, :hour, :minute, :second, :microsecond.
This operation is equivalent to shifting the datetime wall clock
(in other words, the value as someone in that timezone would see
on their watch), then applying the time zone offset to convert it
to UTC, and finally computing the new timezone in case of shifts.
This ensures shift/3 always returns a valid datetime.
On the other hand, time zones that observe "Daylight Saving Time" or other changes, across summer/winter time will add/remove hours from the resulting datetime:
dt = DateTime.new!(~D[2019-03-31], ~T[01:00:00], "Europe/Copenhagen")
DateTime.shift(dt, hour: 1)
#=> #DateTime<2019-03-31 03:00:00+02:00 CEST Europe/Copenhagen>
dt = DateTime.new!(~D[2018-11-04], ~T[00:00:00], "America/Los_Angeles")
DateTime.shift(dt, hour: 2)
#=> #DateTime<2018-11-04 01:00:00-08:00 PST America/Los_Angeles>In case you don't want these changes to happen automatically or you
want to surface time zone conflicts to the user, you can shift
the datetime as a naive datetime and then use from_naive/2:
dt |> NaiveDateTime.shift(duration) |> DateTime.from_naive(dt.time_zone)When using the default ISO calendar, durations are collapsed and applied in the order of months, then seconds and microseconds:
- when shifting by 1 year and 2 months the date is actually shifted by 14 months
- weeks, days and smaller units are collapsed into seconds and microseconds
When shifting by month, days are rounded down to the nearest valid date.
Examples
iex> DateTime.shift(~U[2016-01-01 00:00:00Z], month: 2)
~U[2016-03-01 00:00:00Z]
iex> DateTime.shift(~U[2016-01-01 00:00:00Z], year: 1, week: 4)
~U[2017-01-29 00:00:00Z]
iex> DateTime.shift(~U[2016-01-01 00:00:00Z], minute: -25)
~U[2015-12-31 23:35:00Z]
iex> DateTime.shift(~U[2016-01-01 00:00:00Z], minute: 5, microsecond: {500, 4})
~U[2016-01-01 00:05:00.0005Z]
# leap years
iex> DateTime.shift(~U[2024-02-29 00:00:00Z], year: 1)
~U[2025-02-28 00:00:00Z]
iex> DateTime.shift(~U[2024-02-29 00:00:00Z], year: 4)
~U[2028-02-29 00:00:00Z]
# rounding down
iex> DateTime.shift(~U[2015-01-31 00:00:00Z], month: 1)
~U[2015-02-28 00:00:00Z]shift_zone(datetime, time_zone, time_zone_database \\ Calendar.get_time_zone_database())
(since 1.8.0)@spec shift_zone(t(), Calendar.time_zone(), Calendar.time_zone_database()) :: {:ok, t()} | {:error, :time_zone_not_found | :utc_only_time_zone_database}
Changes the time zone of a DateTime.
Returns a DateTime for the same point in time, but instead at
the time zone provided. It assumes that DateTime is valid and
exists in the given time zone and calendar.
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.
Other time zone databases can be passed as argument or set globally.
See the "Time zone database" section in the module docs.
Examples
iex> {:ok, pacific_datetime} = DateTime.shift_zone(~U[2018-07-16 10:00:00Z], "America/Los_Angeles", FakeTimeZoneDatabase)
iex> pacific_datetime
#DateTime<2018-07-16 03:00:00-07:00 PDT America/Los_Angeles>
iex> DateTime.shift_zone(~U[2018-07-16 10:00:00Z], "bad timezone", FakeTimeZoneDatabase)
{:error, :time_zone_not_found}shift_zone!(datetime, time_zone, time_zone_database \\ Calendar.get_time_zone_database())
(since 1.10.0)@spec shift_zone!(t(), Calendar.time_zone(), Calendar.time_zone_database()) :: t()
Changes the time zone of a DateTime or raises on errors.
See shift_zone/3 for more information.
Examples
iex> DateTime.shift_zone!(~U[2018-07-16 10:00:00Z], "America/Los_Angeles", FakeTimeZoneDatabase)
#DateTime<2018-07-16 03:00:00-07:00 PDT America/Los_Angeles>
iex> DateTime.shift_zone!(~U[2018-07-16 10:00:00Z], "bad timezone", FakeTimeZoneDatabase)
** (ArgumentError) cannot shift ~U[2018-07-16 10:00:00Z] to "bad timezone" time zone, reason: :time_zone_not_found@spec to_date(Calendar.datetime()) :: Date.t()
Converts a DateTime into a Date.
Because Date does not hold time nor time zone 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]@spec to_gregorian_seconds(Calendar.datetime()) :: {integer(), non_neg_integer()}
Converts a DateTime struct to a number of gregorian seconds and microseconds.
Examples
iex> dt = %DateTime{year: 0000, month: 1, day: 1, zone_abbr: "UTC",
...> hour: 0, minute: 0, second: 1, microsecond: {0, 0},
...> utc_offset: 0, std_offset: 0, time_zone: "Etc/UTC"}
iex> DateTime.to_gregorian_seconds(dt)
{1, 0}
iex> dt = %DateTime{year: 2020, month: 5, day: 1, zone_abbr: "UTC",
...> hour: 0, minute: 26, second: 31, microsecond: {5000, 0},
...> utc_offset: 0, std_offset: 0, time_zone: "Etc/UTC"}
iex> DateTime.to_gregorian_seconds(dt)
{63_755_511_991, 5000}
iex> dt = %DateTime{year: 2020, month: 5, day: 1, zone_abbr: "CET",
...> hour: 1, minute: 26, second: 31, microsecond: {5000, 0},
...> utc_offset: 3600, std_offset: 0, time_zone: "Europe/Warsaw"}
iex> DateTime.to_gregorian_seconds(dt)
{63_755_511_991, 5000}@spec to_iso8601(Calendar.datetime(), :basic | :extended, nil | integer()) :: String.t()
Converts the given datetime to ISO 8601:2019 format.
By default, DateTime.to_iso8601/2 returns datetimes formatted in the "extended"
format, for human readability. It also supports the "basic" format through passing the :basic option.
You can also optionally specify an offset for the formatted string.
If none is given, the one in the given datetime is used.
Only supports converting datetimes which are in the ISO calendar. If another calendar is given, it is automatically converted to ISO. It raises if not possible.
WARNING: the ISO 8601 datetime format does not contain the time zone nor its abbreviation, which means information is lost when converting to such format.
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, :extended)
"2000-02-29T23:00:07-04:00"
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, :basic)
"20000229T230007-0400"
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, :extended, 3600)
"2000-03-01T04:00:07+01:00"
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, :extended, 0)
"2000-03-01T03:00:07+00:00"
iex> dt = %DateTime{year: 2000, month: 3, day: 01, zone_abbr: "UTC",
...> hour: 03, minute: 0, second: 7, microsecond: {0, 0},
...> utc_offset: 0, std_offset: 0, time_zone: "Etc/UTC"}
iex> DateTime.to_iso8601(dt, :extended, 0)
"2000-03-01T03:00:07Z"
iex> {:ok, dt, offset} = DateTime.from_iso8601("2000-03-01T03:00:07Z")
iex> "2000-03-01T03:00:07Z" = DateTime.to_iso8601(dt, :extended, offset)@spec to_naive(Calendar.datetime()) :: NaiveDateTime.t()
Converts the given datetime into a NaiveDateTime.
Because NaiveDateTime does not hold time zone information,
any time zone 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]@spec to_string(Calendar.datetime()) :: String.t()
Converts the given datetime to a string according to its calendar.
Unfortunately, there is no standard that specifies rendering of a datetime with its complete time zone information, so Elixir uses a custom (but relatively common) representation which appends the time zone abbreviation and full name to the datetime.
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"
iex> dt = %DateTime{year: -100, month: 12, day: 19, zone_abbr: "CET",
...> hour: 3, minute: 20, second: 31, microsecond: {0, 0},
...> utc_offset: 3600, std_offset: 0, time_zone: "Europe/Stockholm"}
iex> DateTime.to_string(dt)
"-0100-12-19 03:20:31+01:00 CET Europe/Stockholm"@spec to_time(Calendar.datetime()) :: Time.t()
Converts a DateTime into Time.
Because Time does not hold date nor time zone 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]@spec to_unix(Calendar.datetime(), :native | System.time_unit()) :: 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> 1_464_096_368 |> 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@spec truncate(Calendar.datetime(), :microsecond | :millisecond | :second) :: t()
Returns the given datetime with the microsecond field truncated to the given
precision (:microsecond, :millisecond or :second).
The given datetime is returned unchanged if it already has lower precision than the given precision.
Examples
iex> dt1 = %DateTime{year: 2017, month: 11, day: 7, zone_abbr: "CET",
...> hour: 11, minute: 45, second: 18, microsecond: {123456, 6},
...> utc_offset: 3600, std_offset: 0, time_zone: "Europe/Paris"}
iex> DateTime.truncate(dt1, :microsecond)
#DateTime<2017-11-07 11:45:18.123456+01:00 CET Europe/Paris>
iex> dt2 = %DateTime{year: 2017, month: 11, day: 7, zone_abbr: "CET",
...> hour: 11, minute: 45, second: 18, microsecond: {123456, 6},
...> utc_offset: 3600, std_offset: 0, time_zone: "Europe/Paris"}
iex> DateTime.truncate(dt2, :millisecond)
#DateTime<2017-11-07 11:45:18.123+01:00 CET Europe/Paris>
iex> dt3 = %DateTime{year: 2017, month: 11, day: 7, zone_abbr: "CET",
...> hour: 11, minute: 45, second: 18, microsecond: {123456, 6},
...> utc_offset: 3600, std_offset: 0, time_zone: "Europe/Paris"}
iex> DateTime.truncate(dt3, :second)
#DateTime<2017-11-07 11:45:18+01:00 CET Europe/Paris>@spec utc_now(Calendar.calendar() | :native | :microsecond | :millisecond | :second) :: t()
Returns the current datetime in UTC.
If you want the current time in Unix seconds,
use System.os_time/1 instead.
You can also pass a time unit to automatically truncate the resulting datetime. This is available since v1.15.0.
The default unit if none gets passed is :native,
which results on a default resolution of microseconds.
Examples
iex> datetime = DateTime.utc_now()
iex> datetime.time_zone
"Etc/UTC"
iex> datetime = DateTime.utc_now(:second)
iex> datetime.microsecond
{0, 0}@spec utc_now(:native | :microsecond | :millisecond | :second, Calendar.calendar()) :: t()
Returns the current datetime in UTC, supporting a specific calendar and precision.
If you want the current time in Unix seconds,
use System.os_time/1 instead.
Examples
iex> datetime = DateTime.utc_now(:microsecond, Calendar.ISO)
iex> datetime.time_zone
"Etc/UTC"
iex> datetime = DateTime.utc_now(:second, Calendar.ISO)
iex> datetime.microsecond
{0, 0}