View Source DateTime (Elixir v1.10.3)
A datetime implementation with a time zone.
This datetime can be seen as an ephemeral snapshot of a datetime 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.
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.
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.
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 can also be configured. For example, to use the
tzdata database, 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, Tzdata.TimeZoneDatabaseor by calling Calendar.put_time_zone_database/1:
Calendar.put_time_zone_database(Tzdata.TimeZoneDatabase)Link to this section Summary
Functions
Adds a specified amount of time to a DateTime.
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.
Parses the extended "Date and time of day" format described by ISO 8601:2004.
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.
Returns the current datetime in the provided time zone.
Returns the current datetime in the provided time zone or raises on errors
Changes the time zone of a DateTime.
Changes the time zone of a DateTime or raises on errors.
Converts the given datetime to ISO 8601:2004 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.
Link to this section 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() }
Link to this section Functions
add(datetime, amount_to_add, unit \\ :second, time_zone_database \\ Calendar.get_time_zone_database())
View Source (since 1.8.0)@spec add( Calendar.datetime(), integer(), 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 available from System.time_unit/0.
Negative values will move backwards in time.
Takes changes such as summer time/DST into account. This means that adding time can cause the wall time to "go backwards" during "fall back" during autumn. Adding just a few seconds to a datetime just before "spring forward" can cause wall time to increase by more than an hour.
Fractional second precision stays the same in a similar way to NaiveDateTime.add/2.
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>@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(), System.time_unit()) :: integer()
Subtracts datetime2 from datetime1.
The answer can be returned in any unit available from System.time_unit/0.
Leap seconds are not taken into account.
This function returns the difference in seconds where seconds are measured
according to Calendar.ISO.
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.diff(dt1, dt2)
18000
iex> DateTime.diff(dt2, dt1)
-18000@spec from_iso8601(String.t(), Calendar.calendar()) :: {:ok, t(), Calendar.utc_offset()} | {:error, atom()}
Parses the extended "Date and time of day" format described by ISO 8601:2004.
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.
The year parsed by this function is limited to four digits and, while ISO 8601 allows datetimes to specify 24:00:00 as the zero hour of the next day, this notation is not supported by Elixir. 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> 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}from_naive(naive_datetime, time_zone, time_zone_database \\ Calendar.get_time_zone_database())
View Source (since 1.4.0)@spec from_naive( Calendar.naive_datetime(), Calendar.time_zone(), Calendar.time_zone_database() ) :: {:ok, t()} | {:ambiguous, t(), 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. First the one that happens first, then the one that happens after.
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())
View Source (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.
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]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 -62167219200 seconds, which is equivalent to "0000-01-01T00:00:00Z" or 0 Gregorian seconds.
@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]now(time_zone, time_zone_database \\ Calendar.get_time_zone_database())
View Source (since 1.8.0)@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}now!(time_zone, time_zone_database \\ Calendar.get_time_zone_database())
View Source (since 1.10.0)@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_foundshift_zone(datetime, time_zone, time_zone_database \\ Calendar.get_time_zone_database())
View Source (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())
View Source (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_iso8601(Calendar.datetime(), :extended | :basic) :: String.t()
Converts the given datetime to ISO 8601:2004 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.
Only supports converting datetimes which are in the ISO calendar, attempting to convert datetimes from other calendars will raise.
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"@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.
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(), 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()) :: t()
Returns the current datetime in UTC.
Examples
iex> datetime = DateTime.utc_now()
iex> datetime.time_zone
"Etc/UTC"