# `Cldr.DateTime.Interval`
[🔗](https://github.com/elixir-cldr/cldr_dates_times/blob/v2.25.6/lib/cldr/interval/date_time.ex#L1)

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 *date_time* plus a formatting pattern
and use that information to produce a localized formatted string.

See `Cldr.Interval.to_string/3` and `Cldr.DateTime.Interval.to_string/3`.

# `greatest_difference`

Returns the format code representing the date or
time unit that is the greatest difference between
two date/times.

### Arguments

* `from` is any `t:DateTime.t/0` or `t:NaiveDateTine.t/0`

* `to` is any `t:DateTime.t/0` or `t:NaiveDateTine.t/0`

### Returns

* `{:ok, format_code}` where `format_code` is one of

  * `:y` meaning that the greatest difference is in the year
  * `:M` meaning that the greatest difference is in the month
  * `:d` meaning that the greatest difference is in the day
  * `:H` meaning that the greatest difference is in the hour
  * `:m` meaning that the greatest difference is in the minute

* `{:error, :no_practical_difference}`

### Example

    iex> Cldr.DateTime.Interval.greatest_difference(~U[2022-04-22 02:00:00.0Z], ~U[2022-04-22 03:00:00.0Z])
    {:ok, :H}

    iex> Cldr.DateTime.Interval.greatest_difference(~U[2022-04-22 02:00:00.0Z], ~U[2022-04-22 02:00:01.0Z])
    {:error, :no_practical_difference}

# `to_string`

```elixir
@spec to_string(
  Calendar.datetime() | nil,
  Calendar.datetime() | nil,
  Cldr.backend(),
  Keyword.t()
) ::
  {:ok, String.t()} | {:error, {module(), String.t()}}
```

Returns a localised string representing the formatted
interval formed by two dates.

### Arguments

* `from` is any map that conforms to the
  `Calendar.datetime` type.

* `to` is any map that conforms to the
  `Calendar.datetime` type. `to` must occur
  on or after `from`.

* `backend` is any module that includes `use Cldr` and
  is therefore a `Cldr` backend module

* `options` is a keyword list of options. The default is `[]`.

Either of `from` or `to` may also be `nil` in which case the
result is an "open" interval and the non-nil parameter is formatted
using `Cldr.DateTime.to_string/3`.

### Options

* `:format` is one of `:short`, `:medium` or `:long` or a
  format skeleton or a format pattern representating an interval
  format. The default is `:medium`.

* `:date_format` is any one of `:short`, `:medium`, `:long`, `:full`. If defined,
  this option is used to format the date part of the date time. This option is
  only acceptable if the `:format` option is not specified, or is specified as either
  `:short`, `:medium`, `:long`, `:full`. If `:date_format` is not specified
  then the date format is defined by the `:format` option.

* `:time_format` is any one of `:short`, `:medium`, `:long`, `:full`. If defined,
  this option is used to format the time part of the date time. This option is
  only acceptable if the `:format` option is not specified, or is specified as either
  `:short`, `:medium`, `:long`, `:full`. If `:time_format` is not specified
  thenthe time format is defined by the `:format` option.

* `:locale` is any valid locale name returned by `Cldr.known_locale_names/0`
  or a `t:Cldr.LanguageTag.t/0` struct.  The default is `Cldr.get_locale/0`

* `:number_system` a number system into which the formatted date digits should
  be transliterated.

* `:prefer` expresses the preference for one of the possible alternative
  sub-formats. See the variant preference notes below.

### Variant Preference

* A small number of formats have one of two different alternatives, each with their own
  preference specifier. The preferences are specified with the `:prefer` option to
  `Cldr.Date.to_string/3`. The preference is expressed as an atom, or a list of one or two
  atoms with one atom being either `:unicode` or `:ascii` and one atom being either
  `:default` or `:variant`.

  * Some formats (at the time of publishng only time formats but that
    may change in the future) have `:unicode` and `:ascii` versions of the format. The
    difference is the use of ascii space (0x20) as a separateor in the `:ascii` verison
    whereas the `:unicode` version may use non-breaking or other space characters. The
    default is `:unicode` and this is the strongly preferred option. The `:ascii` format
    is primarily to support legacy use cases and is not recommended. See
    `Cldr.Date.available_formats/3` to see which formats have these variants.

  * Some formats (at the time of publishing, only date and datetime formats) have
    `:default` and `:variant` versions of the format. These variant formats are only
    included in a small number of locales. For example, the `:"en-CA"` locale, which has
    a `:default` format respecting typical Canadian formatting and a `:variant` that is
    more closely aligned to US formatting. The default is `:default`.

### Returns

* `{:ok, string}` or

* `{:error, {exception, reason}}`

### Notes

* For more information on interval format patterns
  see the `Cldr.Interval`.

* The available format skeletongs that can be applied are the
  keys of the map returned by `Cldr.DateTime.Format.interval_formats("en", :gregorian)`
  where `"en"` can be replaced by any configuration locale name and `:gregorian`
  is the underlying CLDR calendar type.

* In the case where `from` and `to` are equal, a single
  date is formatted instead of an interval

### Examples

    iex> Cldr.DateTime.Interval.to_string(~U[2020-01-01 00:00:00.0Z],
    ...> ~U[2020-12-31 10:00:00.0Z], MyApp.Cldr)
    {:ok, "Jan 1, 2020, 12:00:00 AM – Dec 31, 2020, 10:00:00 AM"}

    iex> Cldr.DateTime.Interval.to_string(~U[2020-01-01 00:00:00.0Z], nil, MyApp.Cldr)
    {:ok, "Jan 1, 2020, 12:00:00 AM –"}

# `to_string!`

```elixir
@spec to_string!(CalendarInterval.t(), Cldr.backend(), Keyword.t()) ::
  String.t() | no_return()
```

Returns a localised string representing the formatted
interval formed by two dates or raises an
exception.

### Arguments

* `from` is any map that conforms to the
  `Calendar.datetime` type.

* `to` is any map that conforms to the
  `Calendar.datetime` type. `to` must occur
  on or after `from`.

* `backend` is any module that includes `use Cldr` and
  is therefore a `Cldr` backend module.

* `options` is a keyword list of options. The default is `[]`.

### Options

* `:format` is one of `:short`, `:medium` or `:long` or a
  format skeleton or a format pattern representating an interval
  format. The default is `:medium`.

* `:date_format` is any one of `:short`, `:medium`, `:long`, `:full`. If defined,
  this option is used to format the date part of the date time. This option is
  only acceptable if the `:format` option is not specified, or is specified as either
  `:short`, `:medium`, `:long`, `:full`. If `:date_format` is not specified
  then the date format is defined by the `:format` option.

* `:time_format` is any one of `:short`, `:medium`, `:long`, `:full`. If defined,
  this option is used to format the time part of the date time. This option is
  only acceptable if the `:format` option is not specified, or is specified as either
  `:short`, `:medium`, `:long`, `:full`. If `:time_format` is not specified
  then the time format is defined by the `:format` option.

* `:locale` is any valid locale name returned by `Cldr.known_locale_names/0`
  or a `t:Cldr.LanguageTag.t/0` struct.  The default is `Cldr.get_locale/0`.

* `:number_system` a number system into which the formatted date digits should
  be transliterated.

* `:prefer` expresses the preference for one of the possible alternative
  sub-formats. See the variant preference notes below.

### Variant Preference

* A small number of formats have one of two different alternatives, each with their own
  preference specifier. The preferences are specified with the `:prefer` option to
  `Cldr.Date.to_string/3`. The preference is expressed as an atom, or a list of one or two
  atoms with one atom being either `:unicode` or `:ascii` and one atom being either
  `:default` or `:variant`.

  * Some formats (at the time of publishng only time formats but that
    may change in the future) have `:unicode` and `:ascii` versions of the format. The
    difference is the use of ascii space (0x20) as a separateor in the `:ascii` verison
    whereas the `:unicode` version may use non-breaking or other space characters. The
    default is `:unicode` and this is the strongly preferred option. The `:ascii` format
    is primarily to support legacy use cases and is not recommended. See
    `Cldr.Date.available_formats/3` to see which formats have these variants.

  * Some formats (at the time of publishing, only date and datetime formats) have
    `:default` and `:variant` versions of the format. These variant formats are only
    included in a small number of locales. For example, the `:"en-CA"` locale, which has
    a `:default` format respecting typical Canadian formatting and a `:variant` that is
    more closely aligned to US formatting. The default is `:default`.

### Returns

* `formatted_string` or

* raises an exception

### Notes

* For more information on interval format patterns
  see the `Cldr.Interval`.

* The available predefined formats that can be applied are the
  keys of the map returned by `Cldr.DateTime.Format.interval_formats("en", :gregorian)`
  where `"en"` can be replaced by any configuration locale name and `:gregorian`
  is the underlying CLDR calendar type.

* In the case where `from` and `to` are equal, a single
  date is formatted instead of an interval.

### Examples

    iex> use CalendarInterval
    iex> Cldr.DateTime.Interval.to_string!(~I"2020-01-01 00:00/10:00", MyApp.Cldr)
    "Jan 1, 2020, 12:00:00 AM – 10:00:59 AM"

# `to_string!`

Returns a localised string representing the formatted
interval formed by two dates or raises an
exception.

### Arguments

* `from` is any map that conforms to the
  `Calendar.datetime` type.

* `to` is any map that conforms to the
  `Calendar.datetime` type. `to` must occur
  on or after `from`.

* `backend` is any module that includes `use Cldr` and
  is therefore a `Cldr` backend module.

* `options` is a keyword list of options. The default is `[]`.

### Options

* `:format` is one of `:short`, `:medium` or `:long` or a
  format skeleton or a format pattern representating an interval
  format. The default is `:medium`.

* `:date_format` is any one of `:short`, `:medium`, `:long`, `:full`. If defined,
  this option is used to format the date part of the date time. This option is
  only acceptable if the `:format` option is not specified, or is specified as either
  `:short`, `:medium`, `:long`, `:full`. If `:date_format` is not specified
  then the date format is defined by the `:format` option.

* `:time_format` is any one of `:short`, `:medium`, `:long`, `:full`. If defined,
  this option is used to format the time part of the date time. This option is
  only acceptable if the `:format` option is not specified, or is specified as either
  `:short`, `:medium`, `:long`, `:full`. If `:time_format` is not specified
  then the time format is defined by the `:format` option.

* `:locale` is any valid locale name returned by `Cldr.known_locale_names/0`
  or a `t:Cldr.LanguageTag.t/0` struct.  The default is `Cldr.get_locale/0`.

* `:number_system` a number system into which the formatted date digits should
  be transliterated.

* `:prefer` expresses the preference for one of the possible alternative
  sub-formats. See the variant preference notes below.

### Variant Preference

* A small number of formats have one of two different alternatives, each with their own
  preference specifier. The preferences are specified with the `:prefer` option to
  `Cldr.Date.to_string/3`. The preference is expressed as an atom, or a list of one or two
  atoms with one atom being either `:unicode` or `:ascii` and one atom being either
  `:default` or `:variant`.

  * Some formats (at the time of publishng only time formats but that
    may change in the future) have `:unicode` and `:ascii` versions of the format. The
    difference is the use of ascii space (0x20) as a separateor in the `:ascii` verison
    whereas the `:unicode` version may use non-breaking or other space characters. The
    default is `:unicode` and this is the strongly preferred option. The `:ascii` format
    is primarily to support legacy use cases and is not recommended. See
    `Cldr.Date.available_formats/3` to see which formats have these variants.

  * Some formats (at the time of publishing, only date and datetime formats) have
    `:default` and `:variant` versions of the format. These variant formats are only
    included in a small number of locales. For example, the `:"en-CA"` locale, which has
    a `:default` format respecting typical Canadian formatting and a `:variant` that is
    more closely aligned to US formatting. The default is `:default`.

### Returns

* `formatted_string` or

* raises an exception.

### Notes

* For more information on interval format patterns
  see the `Cldr.Interval`.

* The available format skeletons that can be applied are the
  keys of the map returned by `Cldr.DateTime.Format.interval_formats("en", :gregorian)`
  where `"en"` can be replaced by any configuration locale name and `:gregorian`
  is the underlying CLDR calendar type.

* In the case where `from` and `to` are equal, a single
  date is formatted instead of an interval

### Examples

    iex> Cldr.DateTime.Interval.to_string!(~U[2020-01-01 00:00:00.0Z],
    ...> ~U[2020-12-31 10:00:00.0Z], MyApp.Cldr)
    "Jan 1, 2020, 12:00:00 AM – Dec 31, 2020, 10:00:00 AM"

---

*Consult [api-reference.md](api-reference.md) for complete listing*