View Source Date and Time Localization and Formatting

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Note that ex_cldr_dates_times requires Elixir 1.11 or later.

Add ex_cldr_dates_time as a dependency to your mix project:

defp deps do
    {:ex_cldr_dates_times, "~> 2.0"}

then retrieve ex_cldr_dates_times from hex:

mix deps.get
mix deps.compile

Configuring a required backend module

ex_cldr_dates_times uses the configuration set for the dependency ex_cldr. See the documentation for ex_cldr.

A backend module is required that is used to host the functions that manage CLDR data. An example to get started is:

  1. Create a backend module (see ex_cldr for details of the available options). Note the requirement to configure the appropriate Cldr provider backends.

     defmodule MyApp.Cldr do
       use Cldr,
         locales: ["en", "fr", "ja"],
         providers: [Cldr.Number, Cldr.Calendar, Cldr.DateTime]
  2. [Optional] Update config.exs configuration to specify this backend as the system default. Not required, but often useful.

     config :ex_cldr,
       default_locale: "en",
       default_backend: MyApp.Cldr

Migration from Cldr.DatesTimes Version 1

  1. In modules where there are calls to Cldr.DateTime.to_string/2 (or the Date and Time equivalents), add alias MyApp.Cldr to the top of the module. That will ensure that calls are directed to the backend with minimal code change. This is the preferred approach.

  2. Alternatively, update any calls to Cldr.Date.to_string/2 to call Cldr.Date.to_string/3 with the second parameter being a backend module. The same applies for migrating to Cldr.DateTime.to_string/3, Cldr.Time.to_string/3 and Cldr.DateTime.Relative.to_string/3. For example:

     # Change from to_string/2 to to_string/3
     # Old version
     iex> Cldr.DateTime.to_string ~U[2020-05-30 03:52:56Z], format: :short
     # New version. Note the addition of a backend module as
     # the second parameter.
     iex> Cldr.DateTime.to_string ~U[2020-05-30 03:52:56Z], MyApp.Cldr, format: :short

Usage Introduction

ex_cldr_dates_times is an addon library application for ex_cldr that provides localisation and formatting for dates, times and date_times.

The primary api is MyApp.Cldr.Date.to_string/2, MyApp.Cldr.Time.to_string/2, MyApp.Cldr.DateTime.to_string/2 and MyApp.Cldr.DateTime.Relative.to_string/2. In the following examples MyApp refers to a CLDR backend module that must be defined by the developer:

iex> MyApp.Cldr.Date.to_string ~D[2020-05-30]
{:ok, "May 30, 2020"}

iex> MyApp.Cldr.Time.to_string ~U[2020-05-30 03:52:56Z]
{:ok, "3:52:56 AM"}

iex> MyApp.Cldr.DateTime.to_string ~U[2020-05-30 03:52:56Z]
{:ok, "May 30, 2020, 3:52:56 AM"}

# Note that if options are provided, a backend
# module is also required
iex> MyApp.Cldr.DateTime.Relative.to_string 1, unit: :day, format: :narrow
{:ok, "tomorrow"}

For help in iex:

iex> h MyApp.Cldr.Date.to_string
iex> h MyApp.Cldr.Time.to_string
iex> h MyApp.Cldr.DateTime.to_string
iex> h MyApp.Cldr.DateTime.Relative.to_string

Date, Time and DateTime Localization Formatting

Dates, Times and DateTimes can be formatted using:

  • The format types defined for each locale. These format types provide cross-locale standardisation and therefore should be preferred where possible. The format types, implemented for MyApp.Cldr.Date.to_string/2, MyApp.Cldr.Time.to_string/2,MyApp.Cldr.DateTime.to_string/2 are :short, :medium, :long and :full. The default is :medium. For example, assuming a configured backend called MyApp.Cldr:

      iex> MyApp.Cldr.DateTime.to_string ~U[2020-05-30 03:52:56Z], format: :short
      {:ok, "5/30/20, 3:52 AM"}
      iex> MyApp.Cldr.DateTime.to_string ~U[2020-05-30 03:52:56Z], format: :long
      {:ok, "May 30, 2020 at 3:52:56 AM UTC"}
      iex> MyApp.Cldr.DateTime.to_string ~U[2020-05-30 03:52:56Z], format: :medium
      {:ok, "May 30, 2020, 3:52:56 AM"}
      iex> MyApp.Cldr.DateTime.to_string ~U[2020-05-30 03:52:56Z], format: :long, locale: "fr"
      {:ok, "30 mai 2020 à 03:52:56 UTC"}
  • A user specified format string. A format string uses one or more formatting symbols to define what date and time elements should be places in the format. A simple example to format the time into hours and minutes:

      iex> MyApp.Cldr.DateTime.to_string ~U[2020-05-30 03:52:56Z], format: "hh:mm"
      {:ok, "03:52"}
  • For DateTimes there is also a set of predefined format name. These format names are returned by MyApp.Cldr.DateTime.Format.date_time_available_formats/0 (assuming your backend is MyApp.Cldr). The set of common format names across all locales configured in ex_cldr can be returned by Cldr.DateTime.Format.common_date_time_format_names. These format names can be used with the :format parameter to Cldr.DateTime.to_string/2 module only.

      iex> MyApp.Cldr.DateTime.Format.date_time_available_formats
      %{mmmm_w_count_one: "'week' W 'of' MMMM", gy_mmm: "MMM y G", md: "M/d",
      mmm_md: "MMMM d", e_hms: "E HH:mm:ss", ed: "d E", y_mmm: "MMM y",
      e_hm: "E HH:mm", mmm_ed: "E, MMM d", y_mmm_ed: "E, MMM d, y",
      gy_mm_md: "MMM d, y G", mmm: "LLL", y_md: "M/d/y", gy: "y G",
      hms: "h:mm:ss a", hm: "h:mm a", y_mmmm: "MMMM y", m: "L",
      gy_mmm_ed: "E, MMM d, y G", y_qqq: "QQQ y", e: "ccc", y_qqqq: "QQQQ y",
      hmsv: "h:mm:ss a v", mmmm_w_count_other: "'week' W 'of' MMMM",
      ehm: "E h:mm a", y_m_ed: "E, M/d/y", h: "h a", hmv: "h:mm a v",
      yw_count_other: "'week' w 'of' y", mm_md: "MMM d", y_m: "M/y", m_ed: "E, M/d",
      ms: "mm:ss", d: "d", y_mm_md: "MMM d, y", yw_count_one: "'week' w 'of' y",
      y: "y", ehms: "E h:mm:ss a"}
      # These format types can be invoked for any locale - meaning
      # these format names are defined for all configured locales.
      iex> Cldr.DateTime.Format.common_date_time_format_names(MyApp.Cldr)
      [:gy_mmm, :md, :mmm_md, :e_hms, :ed, :y_mmm, :e_hm, :mmm_ed, :y_mmm_ed,
      :gy_mm_md, :mmm, :y_md, :gy, :hms, :hm, :y_mmmm, :m, :gy_mmm_ed, :y_qqq, :e,
      :y_qqqq, :hmsv, :mmmm_w_count_other, :ehm, :y_m_ed, :h, :hmv, :yw_count_other,
      :mm_md, :y_m, :m_ed, :ms, :d, :y_mm_md, :y, :ehms]
      iex> Cldr.DateTime.to_string ~U[2020-05-30 03:52:56Z], MyApp.Cldr, format: :gy_mmm_ed
      {:ok, "Sat, May 30, 2020 AD"}

Format strings

The CLDR standard defines a wide range of format symbols. Most - but not all - of these symbols are supported in Cldr. The supported symbols are described below. Note the known restrictions and limitations.

ElementSymbolExampleCldr Format
EraG, GG, GGG"AD"Abbreviated
GGGG"Anno Domini"Wide
Yeary7Minimum necessary digits
yy"17"Least significant 2 digits
yyy"017", "2017"Padded to at least 3 digits
yyyy"2017"Padded to at least 4 digits
yyyyy"02017"Padded to at least 5 digits
ISOWeek YearY7Minimum necessary digits
YY"17"Least significant 2 digits
YYY"017", "2017"Padded to at least 3 digits
YYYY"2017"Padded to at least 4 digits
YYYYY"02017"Padded to at least 5 digits
Related Gregorian Yearr, rr, rr+2017Minimum necessary digits
Cyclic YearU, UU, UUU"甲子"Abbreviated
UUUU"甲子" (for now)Wide
UUUUU"甲子" (for now)Narrow
Extended Yearu+4601Minimim necessary digits
QuarterQ2Single digit
QQ"02"Two digits
QQQQ"2nd quarter"Wide
Standalone Quarterq2Single digit
qq"02"Two digits
qqqq"2nd quarter"Wide
MonthM9Single digit
MM"09"Two digits
Standalone MonthL9Single digit
LL"09"Two digits
Week of Yearw2, 22Single digit
ww02, 22Two digits, zero padded
Week of MonthW2Single digit. NOT IMPLEMENTED YET
Day of YearD3, 33, 333Minimum necessary digits
DD03, 33, 333Minimum of 2 digits, zero padded
DDD003, 033, 333Minimum of 3 digits, zero padded
Day of Monthd2, 22Minimum necessary digits
dd02, 22Two digits, zero padded
Day of WeekE, EE, EEE"Tue"Abbreviated
e2Single digit
ee"02"Two digits
Standalone Day of Weekc, cc2Single digit
AM or PMa, aa, aaa"am."Abbreviated
Noon, Mid, AM, PMb, bb, bbb"mid."Abbreviated
Flexible time periodB, BB, BBB"at night"Abbreviated
BBBB"at night"Wide
BBBBB"at night"Narrow
Hourh, K, H, kSee the table below
Minutem3, 10Minimim digits of minutes
mm"03", "12"Two digits, zero padded
Seconds3, 48Minimim digits of seconds
ss"03", "48"Two digits, zero padded
Fractional SecondsS3, 48Minimim digits of fractional seconds
SS"03", "48"Two digits, zero padded
MillisecondsA+4000, 63241Minimim digits of milliseconds since midnight
Generic non-location TZv"Etc/UTC":time_zone key, unlocalised
vvvv"unk"Generic timezone name. Currently returns only "unk"
Specific non-location TZz..zzz"UTC":zone_abbr key, unlocalised
zzzz"GMT"Delegates to zone_gmt/4
Timezone IDV"unk":zone_abbr key, unlocalised
VV"Etc/UTCDelegates to zone_gmt/4
VVV"Unknown City"Exemplar city. Not supported.
VVVV"GMT"Delegates to `zone_gmt/4
ISO8601 FormatZ..ZZZ"+0100"ISO8601 Basic Format with hours and minutes
ZZZZ"+01:00"Delegates to `zone_gmt/4
ZZZZZ"+01:00:10"ISO8601 Extended format with optional seconds
ISO8601 plus ZX"+01"ISO8601 Basic Format with hours and optional minutes or "Z"
XX"+0100"ISO8601 Basic Format with hours and minutes or "Z"
XXX"+0100"ISO8601 Basic Format with hours and minutes, optional seconds or "Z"
XXXX"+010059"ISO8601 Basic Format with hours and minutes, optional seconds or "Z"
XXXXX"+01:00:10"ISO8601 Extended Format with hours and minutes, optional seconds or "Z"
ISO8601 minus Zx"+0100"ISO8601 Basic Format with hours and optional minutes
xx"-0800"ISO8601 Basic Format with hours and minutes
xxx"+01:00"ISO8601 Extended Format with hours and minutes
xxxx"+010059"ISO8601 Basic Format with hours and minutes, optional seconds
xxxxx"+01:00:10"ISO8601 Extended Format with hours and minutes, optional seconds
GMT FormatO"+0100"Short localised GMT format
OOOO"+010059"Long localised GMT format

Formatting symbols for hour of day

The hour of day can be formatted differently depending whether a 12- or 24-hour day is being represented and depending on the way in which midnight and noon are represented. The following table illustrates the differences:


Relative Date, Time and DateTime Localization Formatting

The primary API for formatting relative dates and datetimes is MyApp.Cldr.DateTime.Relative.to_string/2. Some examples:

iex> MyApp.Cldr.DateTime.Relative.to_string(-1)
{:ok, "1 second ago"}

iex> MyApp.Cldr.DateTime.Relative.to_string(1)
{:ok, "in 1 second"}

iex> MyApp.Cldr.DateTime.Relative.to_string(1, unit: :day)
{:ok, "tomorrow"}

iex> MyApp.Cldr.DateTime.Relative.to_string(1, unit: :day, locale: "fr")
{:ok, "demain"}

iex> MyApp.Cldr.DateTime.Relative.to_string(1, unit: :day, format: :narrow)
{:ok, "tomorrow"}

iex> MyApp.Cldr.DateTime.Relative.to_string(1234, unit: :year)
{:ok, "in 1,234 years"}

iex> MyApp.Cldr.DateTime.Relative.to_string(1234, unit: :year, locale: "fr")
{:ok, "dans 1 234 ans"}

iex> MyApp.Cldr.DateTime.Relative.to_string(31)
{:ok, "in 31 seconds"}

iex> MyApp.Cldr.DateTime.Relative.to_string(~D[2017-04-29], relative_to: ~D[2017-04-26])
{:ok, "in 3 days"}

iex> MyApp.Cldr.DateTime.Relative.to_string(310, format: :short, locale: "fr")
{:ok, "dans 5 min"}

iex> MyApp.Cldr.DateTime.Relative.to_string(310, format: :narrow, locale: "fr")
{:ok, "+5 min"}

iex> MyApp.Cldr.DateTime.Relative.to_string 2, unit: :wed, format: :short
{:ok, "in 2 Wed."}

iex> MyApp.Cldr.DateTime.Relative.to_string 1, unit: :wed, format: :short
{:ok, "next Wed."}

iex> MyApp.Cldr.DateTime.Relative.to_string -1, unit: :wed, format: :short
{:ok, "last Wed."}

iex> MyApp.Cldr.DateTime.Relative.to_string -1, unit: :wed
{:ok, "last Wednesday"}

iex> MyApp.Cldr.DateTime.Relative.to_string -1, unit: :quarter
{:ok, "last quarter"}

iex> MyApp.Cldr.DateTime.Relative.to_string -1, unit: :mon, locale: "fr"
{:ok, "lundi dernier"}

iex> MyApp.Cldr.DateTime.Relative.to_string(~D[2017-04-29], unit: :ziggeraut)
{:error, {Cldr.UnknownTimeUnit,
"Unknown time unit :ziggeraut.  Valid time units are [:day, :hour, :minute, :month, :second, :week, :year, :mon, :tue, :wed, :thu, :fri, :sat, :sun, :quarter]"}}

Interval Formatting

Interval formats allow for software to format intervals like "Jan 10-12, 2008" as a shorter and more natural format than "Jan 10, 2008 - Jan 12, 2008". They are designed to take a start and end date, time or datetime plus a formatting pattern and use that information to produce a localized format.

An interval is expressed as either a from and to date, time or datetime. Or it can also be a Date.Range or CalendarInterval from the calendar_interval library.

Cldr.Interval.to_string/3 function to format an interval based upon the type of the arguments: date, datetime or time. The modules Cldr.Date.Interval, Cldr.Time.Interval and Cldr.DateTime.Interval also provide a to_string/3 function for when the desired output format is more specific.

Some examples:

iex> Cldr.Interval.to_string ~D[2020-01-01], ~D[2020-12-31], MyApp.Cldr
{:ok, "Jan 1 – Dec 31, 2020"}

iex> Cldr.Interval.to_string ~D[2020-01-01], ~D[2020-01-12], MyApp.Cldr
{:ok, "Jan 1 – 12, 2020"}

iex> Cldr.Interval.to_string ~D[2020-01-01], ~D[2020-01-12], MyApp.Cldr,
...> format: :long
{:ok, "Wed, Jan 1 – Sun, Jan 12, 2020"}

iex> Cldr.Interval.to_string ~D[2020-01-01], ~D[2020-12-01], MyApp.Cldr,
...> format: :long, style: :year_and_month
{:ok, "January – December 2020"}

iex> use CalendarInterval
iex> Cldr.Interval.to_string ~I"2020-01-01/12", MyApp.Cldr,
...> format: :long
{:ok, "Wed, Jan 1 – Sun, Jan 12, 2020"}

iex> Cldr.Interval.to_string ~U[2020-01-01 00:00:00.0Z], ~U[2020-12-01 10:05:00.0Z], MyApp.Cldr,
...> format: :long
{:ok, "January 1, 2020 at 12:00:00 AM UTC – December 1, 2020 at 10:05:00 AM UTC"}

iex> Cldr.Interval.to_string ~U[2020-01-01 00:00:00.0Z], ~U[2020-01-01 10:05:00.0Z], MyApp.Cldr,
...> format: :long
{:ok, "January 1, 2020 at 12:00:00 AM UTC – 10:05:00 AM UTC"}

Known restrictions and limitations

Although largely complete (with respect to the CLDR data), there are some known limitations as of release 2.0.

  • Timezones Although the timezone format codes are supported (formatting symbols v, V, x, X, z, Z, O) not all localisations are performed. Only that data available within a DateTime struct is used to format timezone data.