A Date struct and functions.
The Date struct contains the fields year, month, day and calendar. New dates can be built with the new/3 function or using the ~D sigil:
iex> ~D[2000-01-01]
~D[2000-01-01]Both new/3 and sigil return a struct where the date fields can be accessed directly:
iex> date = ~D[2000-01-01]
iex> date.year
2000
iex> date.month
1The functions on this module work with the Date struct as well as any struct that contains the same fields as the Date struct, such as NaiveDateTime and DateTime. Such functions expect Calendar.date/0 in their typespecs (instead of t/0).
Developers should avoid creating the Date structs directly and instead rely on the functions provided by this module as well as the ones in 3rd party calendar libraries.
Comparisons in Elixir using ==, >, < and similar are structural and based on the Date struct fields. For proper comparison between dates, use the compare/2 function.
The add/2 and diff/2 functions can be used for computing dates or retrieving the number of days between instants. For example, if there is an interest in computing the number of days from the Unix epoch (1970-01-01):
iex> Date.diff(~D[2010-04-17], ~D[1970-01-01])
14716
iex> Date.add(~D[1970-01-01], 14716)
~D[2010-04-17]Those functions are optimized to deal with common epochs, such as the Unix Epoch above or the Gregorian Epoch (0000-01-01).
Adds the number of days to the given date
Compares two date structs
Converts the given date from its calendar to the given calendar
Similar to Date.convert/2, but raises an ArgumentError if the conversion between the two calendars is not possible
Calculates the day of the week of a given date
Returns the number of days in the given date month
Calculates the difference between two dates, in a full number of days
Converts an Erlang date tuple to a Date struct
Converts an Erlang date tuple but raises for invalid dates
Parses the extended “Dates” format described by ISO 8601:2004
Parses the extended “Dates” format described by ISO 8601:2004
Returns true if the year in the given date is a leap year
Builds a new ISO date
Returns a range of dates
Converts the given date to an Erlang date tuple
Converts the given date to ISO 8601:2004
Converts the given date to a string according to its calendar
Returns the current date in UTC
t() :: %Date{calendar: Calendar.calendar(), day: Calendar.day(), month: Calendar.month(), year: Calendar.year()} add(Calendar.date(), integer()) :: t()
Adds the number of days to the given date.
The days are counted as Gregorian days. The date is returned in the same calendar as it was given in.
iex> Date.add(~D[2000-01-03], -2)
~D[2000-01-01]
iex> Date.add(~D[2000-01-01], 2)
~D[2000-01-03]
iex> Date.add(~N[2000-01-01 09:00:00], 2)
~D[2000-01-03]compare(Calendar.date(), Calendar.date()) :: :lt | :eq | :gt
Compares two date structs.
Returns :gt if first date is later than the second and :lt for vice versa. If the two dates are equal :eq is returned.
iex> Date.compare(~D[2016-04-16], ~D[2016-04-28])
:ltThis function can also be used to compare across more complex calendar types by considering only the date fields:
iex> Date.compare(~D[2016-04-16], ~N[2016-04-28 01:23:45])
:lt
iex> Date.compare(~D[2016-04-16], ~N[2016-04-16 01:23:45])
:eq
iex> Date.compare(~N[2016-04-16 12:34:56], ~N[2016-04-16 01:23:45])
:eqconvert(Calendar.date(), Calendar.calendar()) :: {:ok, t()} | {:error, :incompatible_calendars}
Converts the given date from its calendar to the given calendar.
Returns {:ok, date} if the calendars are compatible, or {:error, :incompatible_calendars} if they are not.
See also Calendar.compatible_calendars?/2.
Imagine someone implements Calendar.Holocene, a calendar based on the Gregorian calendar that adds exactly 10,000 years to the current Gregorian year:
iex> Date.convert(~D[2000-01-01], Calendar.Holocene)
{:ok, %Date{calendar: Calendar.Holocene, year: 12000, month: 1, day: 1}}convert!(Calendar.date(), Calendar.calendar()) :: t()
Similar to Date.convert/2, but raises an ArgumentError if the conversion between the two calendars is not possible.
Imagine someone implements Calendar.Holocene, a calendar based on the Gregorian calendar that adds exactly 10,000 years to the current Gregorian year:
iex> Date.convert!(~D[2000-01-01], Calendar.Holocene)
%Date{calendar: Calendar.Holocene, year: 12000, month: 1, day: 1}day_of_week(Calendar.date()) :: non_neg_integer()
Calculates the day of the week of a given date.
Returns the day of the week as an integer. For the ISO 8601 calendar (the default), it is an integer from 1 to 7, where 1 is Monday and 7 is Sunday.
iex> Date.day_of_week(~D[2016-10-31])
1
iex> Date.day_of_week(~D[2016-11-01])
2
iex> Date.day_of_week(~N[2016-11-01 01:23:45])
2days_in_month(Calendar.date()) :: Calendar.day()
Returns the number of days in the given date month.
iex> Date.days_in_month(~D[1900-01-13])
31
iex> Date.days_in_month(~D[1900-02-09])
28
iex> Date.days_in_month(~N[2000-02-20 01:23:45])
29diff(Calendar.date(), Calendar.date()) :: integer()
Calculates the difference between two dates, in a full number of days.
It returns the number of Gregorian days between the dates. Only Date structs that follow the same or compatible calendars can be compared this way. If two calendars are not compatible, it will raise.
iex> Date.diff(~D[2000-01-03], ~D[2000-01-01])
2
iex> Date.diff(~D[2000-01-01], ~D[2000-01-03])
-2
iex> Date.diff(~D[2000-01-01], ~N[2000-01-03 09:00:00])
-2from_erl(:calendar.date(), Calendar.calendar()) :: {:ok, t()} | {:error, atom()}
Converts an Erlang date tuple to a Date struct.
Only supports converting dates which are in the ISO calendar, or other calendars in which the days also start at midnight. Attempting to convert dates from other calendars will return an error tuple.
iex> Date.from_erl({2000, 1, 1})
{:ok, ~D[2000-01-01]}
iex> Date.from_erl({2000, 13, 1})
{:error, :invalid_date}from_erl!(:calendar.date(), Calendar.calendar()) :: t()
Converts an Erlang date tuple but raises for invalid dates.
iex> Date.from_erl!({2000, 1, 1})
~D[2000-01-01]
iex> Date.from_erl!({2000, 13, 1})
** (ArgumentError) cannot convert {2000, 13, 1} to date, reason: :invalid_datefrom_iso8601(String.t(), Calendar.calendar()) :: {:ok, t()} | {:error, atom()}
Parses the extended “Dates” format described by ISO 8601:2004.
iex> Date.from_iso8601("2015-01-23")
{:ok, ~D[2015-01-23]}
iex> Date.from_iso8601("2015:01:23")
{:error, :invalid_format}
iex> Date.from_iso8601("2015-01-32")
{:error, :invalid_date}from_iso8601!(String.t(), Calendar.calendar()) :: t()
Parses the extended “Dates” format described by ISO 8601:2004.
Raises if the format is invalid.
iex> Date.from_iso8601!("2015-01-23")
~D[2015-01-23]
iex> Date.from_iso8601!("2015:01:23")
** (ArgumentError) cannot parse "2015:01:23" as date, reason: :invalid_formatleap_year?(Calendar.date()) :: boolean()
Returns true if the year in the given date is a leap year.
iex> Date.leap_year?(~D[2000-01-01])
true
iex> Date.leap_year?(~D[2001-01-01])
false
iex> Date.leap_year?(~D[2004-01-01])
true
iex> Date.leap_year?(~D[1900-01-01])
false
iex> Date.leap_year?(~N[2004-01-01 01:23:45])
truenew(Calendar.year(), Calendar.month(), Calendar.day(), Calendar.calendar()) :: {:ok, t()} | {:error, atom()}
Builds a new ISO date.
Expects all values to be integers. Returns {:ok, date} if each entry fits its appropriate range, returns {:error, reason} otherwise.
iex> Date.new(2000, 1, 1)
{:ok, ~D[2000-01-01]}
iex> Date.new(2000, 13, 1)
{:error, :invalid_date}
iex> Date.new(2000, 2, 29)
{:ok, ~D[2000-02-29]}
iex> Date.new(2000, 2, 30)
{:error, :invalid_date}
iex> Date.new(2001, 2, 29)
{:error, :invalid_date}range(Date.t(), Date.t()) :: Date.Range.t()
Returns a range of dates.
A range of dates represents a discrete number of dates where the first and last values are dates with matching calendars.
Ranges of dates can be either increasing (first <= last) or decreasing (first > last). They are also always inclusive.
iex> Date.range(~D[1999-01-01], ~D[2000-01-01])
#DateRange<~D[1999-01-01], ~D[2000-01-01]>A range of dates implements the Enumerable protocol, which means functions in the Enum module can be used to work with ranges:
iex> range = Date.range(~D[2001-01-01], ~D[2002-01-01])
iex> Enum.count(range)
366
iex> Enum.member?(range, ~D[2001-02-01])
true
iex> Enum.reduce(range, 0, fn _date, acc -> acc - 1 end)
-366to_erl(Calendar.date()) :: :calendar.date()
Converts the given date to an Erlang date tuple.
Only supports converting dates which are in the ISO calendar, or other calendars in which the days also start at midnight. Attempting to convert dates from other calendars will raise.
iex> Date.to_erl(~D[2000-01-01])
{2000, 1, 1}
iex> Date.to_erl(~N[2000-01-01 00:00:00])
{2000, 1, 1}to_iso8601(Calendar.date(), :extended | :basic) :: String.t()
Converts the given date to ISO 8601:2004.
By default, Date.to_iso8601/2 returns dates formatted in the “extended” format, for human readability. It also supports the “basic” format through passing the :basic option.
Only supports converting dates which are in the ISO calendar, or other calendars in which the days also start at midnight. Attempting to convert dates from other calendars will raise an ArgumentError.
iex> Date.to_iso8601(~D[2000-02-28])
"2000-02-28"
iex> Date.to_iso8601(~D[2000-02-28], :basic)
"20000228"
iex> Date.to_iso8601(~N[2000-02-28 00:00:00])
"2000-02-28"to_string(Calendar.date()) :: String.t()
Converts the given date to a string according to its calendar.
iex> Date.to_string(~D[2000-02-28])
"2000-02-28"
iex> Date.to_string(~N[2000-02-28 01:23:45])
"2000-02-28"utc_today(Calendar.calendar()) :: t()
Returns the current date in UTC.
iex> date = Date.utc_today()
iex> date.year >= 2016
true
© 2012 Plataformatec
Licensed under the Apache License, Version 2.0.
https://hexdocs.pm/elixir/1.6.0/Date.html