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

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"}

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"}}

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

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.

Time representations with reduced accuracy are not supported.

Note that 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.

Examples

iex> {:ok, datetime, 0} = DateTime.from_iso8601("2015-01-23T23:50:07Z")
iex> datetime
#DateTime<2015-01-23 23:50:07Z>

iex> {:ok, datetime, 9000} = DateTime.from_iso8601("2015-01-23T23:50:07.123+02:30")
iex> datetime
#DateTime<2015-01-23 21:20:07.123Z>

iex> {:ok, datetime, 9000} = DateTime.from_iso8601("2015-01-23T23:50:07,123+02:30")
iex> datetime
#DateTime<2015-01-23 21:20:07.123Z>

iex> {:ok, datetime, 0} = DateTime.from_iso8601("-2015-01-23T23:50:07Z")
iex> datetime
#DateTime<-2015-01-23 23:50:07Z>

iex> {:ok, datetime, 9000} = DateTime.from_iso8601("-2015-01-23T23:50:07,123+02:30")
iex> datetime
#DateTime<-2015-01-23 21:20:07.123Z>

iex> DateTime.from_iso8601("2015-01-23P23:50:07")
{:error, :invalid_format}
iex> DateTime.from_iso8601("2015-01-23 23:50:07A")
{: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}
iex> DateTime.from_iso8601("2015-01-23T23:50:07.123-00:60")
{:error, :invalid_format}

Converts the given NaiveDateTime to DateTime.

It expects a time zone to put the NaiveDateTime in. Currently it only supports “Etc/UTC” as time zone.

Examples

iex> DateTime.from_naive!(~N[2016-05-24 13:26:08.003], "Etc/UTC")
#DateTime<2016-05-24 13:26:08.003Z>

Converts the given NaiveDateTime to DateTime.

It expects a time zone to put the NaiveDateTime in. Currently it only supports “Etc/UTC” as time zone.

Examples

iex> {:ok, datetime} = DateTime.from_naive(~N[2016-05-24 13:26:08.003], "Etc/UTC")
iex> datetime
#DateTime<2016-05-24 13:26:08.003Z>

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)
#DateTime<1970-01-01 00:00:00Z>

iex> DateTime.from_unix!(1_464_096_368)
#DateTime<2016-05-24 13:26:08Z>

iex> DateTime.from_unix!(1_432_560_368_868_569, :microsecond)
#DateTime<2015-05-25 13:26:08.868569Z>

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
#DateTime<2016-05-24 13:26:08Z>

iex> {:ok, datetime} = DateTime.from_unix(1_432_560_368_868_569, :microsecond)
iex> datetime
#DateTime<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
#DateTime<6403-03-17 07:05:22.320Z>

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

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]

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"

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]

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"

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]

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

Returns the given datetime with the microsecond field truncated to the given precision (:microsecond, millisecond or :second).

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>

Returns the current datetime in UTC.

Examples

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