[[mapping-date-format]]
=== `format`

In JSON documents, dates are represented as strings. Elasticsearch uses a set
of preconfigured formats to recognize and parse these strings into a long
value representing _milliseconds-since-the-epoch_ in UTC.

Besides the <<built-in-date-formats,built-in formats>>, your own
<<custom-date-formats,custom formats>> can be specified using the familiar
`yyyy/MM/dd` syntax:

[source,console]
--------------------------------------------------
PUT my-index-000001
{
  "mappings": {
    "properties": {
      "date": {
        "type":   "date",
        "format": "yyyy-MM-dd"
      }
    }
  }
}
--------------------------------------------------

Many APIs which support date values also support <<date-math,date math>>
expressions, such as `now-1m/d` -- the current time, minus one month, rounded
down to the nearest day.

[[custom-date-formats]]
==== Custom date formats

Completely customizable date formats are supported. The syntax for these is explained
https://docs.oracle.com/javase/8/docs/api/java/time/format/DateTimeFormatter.html[DateTimeFormatter docs].

[[built-in-date-formats]]
==== Built In Formats

Most of the below formats have a `strict` companion format, which means that
year, month and day parts of the week must use respectively 4, 2 and 2 digits
exactly, potentially prepending zeros. For instance a date like `5/11/1` would
be considered invalid and would need to be rewritten to `2005/11/01` to be
accepted by the date parser.

To use them, you need to prepend `strict_` to the name of the date format, for
instance `strict_date_optional_time` instead of `date_optional_time`.

These strict date formats are especially useful when
<<date-detection,date fields are dynamically mapped>> in order to make sure to
not accidentally map irrelevant strings as dates.

The following tables lists all the defaults ISO formats supported:

`epoch_millis`::

    A formatter for the number of milliseconds since the epoch. Note, that
    this timestamp is subject to the limits of a Java `Long.MIN_VALUE` and
    `Long.MAX_VALUE`.

`epoch_second`::

    A formatter for the number of seconds since the epoch. Note, that this
    timestamp is subject to the limits of a Java `Long.MIN_VALUE` and `Long.
    MAX_VALUE` divided by 1000 (the number of milliseconds in a second).

[[strict-date-time]]`date_optional_time` or `strict_date_optional_time`::

    A generic ISO datetime parser, where the date must include the year at a minimum, and the time
    (separated by `T`), is optional.
    Examples: `yyyy-MM-dd'T'HH:mm:ss.SSSZ` or  `yyyy-MM-dd`.

[[strict-date-time-nanos]]`strict_date_optional_time_nanos`::

    A generic ISO datetime parser, where the date must include the year at a minimum, and the time
    (separated by `T`), is optional. The fraction of a second
    part has a nanosecond resolution.
    Examples: `yyyy-MM-dd'T'HH:mm:ss.SSSSSSZ` or  `yyyy-MM-dd`.

`basic_date`::

    A basic formatter for a full date as four digit year, two digit month of
    year, and two digit day of month: `yyyyMMdd`.

`basic_date_time`::

    A basic formatter that combines a basic date and time, separated by a 'T':
    `yyyyMMdd'T'HHmmss.SSSZ`.

`basic_date_time_no_millis`::

    A basic formatter that combines a basic date and time without millis,
    separated by a 'T': `yyyyMMdd'T'HHmmssZ`.

`basic_ordinal_date`::

    A formatter for a full ordinal date, using a four digit year and three
    digit dayOfYear: `yyyyDDD`.

`basic_ordinal_date_time`::

    A formatter for a full ordinal date and time, using a four digit year and
    three digit dayOfYear: `yyyyDDD'T'HHmmss.SSSZ`.

`basic_ordinal_date_time_no_millis`::

    A formatter for a full ordinal date and time without millis, using a four
    digit year and three digit dayOfYear: `yyyyDDD'T'HHmmssZ`.

`basic_time`::

    A basic formatter for a two digit hour of day, two digit minute of hour,
    two digit second of minute, three digit millis, and time zone offset:
    `HHmmss.SSSZ`.

`basic_time_no_millis`::

    A basic formatter for a two digit hour of day, two digit minute of hour,
    two digit second of minute, and time zone offset: `HHmmssZ`.

`basic_t_time`::

    A basic formatter for a two digit hour of day, two digit minute of hour,
    two digit second of minute, three digit millis, and time zone off set
    prefixed by 'T': `'T'HHmmss.SSSZ`.

`basic_t_time_no_millis`::

    A basic formatter for a two digit hour of day, two digit minute of hour,
    two digit second of minute, and time zone offset prefixed by 'T':
    `'T'HHmmssZ`.

`basic_week_date` or `strict_basic_week_date`::

    A basic formatter for a full date as four digit weekyear, two digit week
    of weekyear, and one digit day of week: `xxxx'W'wwe`.

`basic_week_date_time` or `strict_basic_week_date_time`::

    A basic formatter that combines a basic weekyear date and time, separated
    by a 'T': `xxxx'W'wwe'T'HHmmss.SSSZ`.

`basic_week_date_time_no_millis` or `strict_basic_week_date_time_no_millis`::

    A basic formatter that combines a basic weekyear date and time without
    millis, separated by a 'T': `xxxx'W'wwe'T'HHmmssZ`.

`date` or `strict_date`::

    A formatter for a full date as four digit year, two digit month of year,
    and two digit day of month: `yyyy-MM-dd`.

`date_hour` or `strict_date_hour`::

    A formatter that combines a full date and two digit hour of day:
    `yyyy-MM-dd'T'HH`.

`date_hour_minute` or `strict_date_hour_minute`::

    A formatter that combines a full date, two digit hour of day, and two
    digit minute of hour: `yyyy-MM-dd'T'HH:mm`.

`date_hour_minute_second` or `strict_date_hour_minute_second`::

    A formatter that combines a full date, two digit hour of day, two digit
    minute of hour, and two digit second of minute: `yyyy-MM-dd'T'HH:mm:ss`.

`date_hour_minute_second_fraction` or `strict_date_hour_minute_second_fraction`::

    A formatter that combines a full date, two digit hour of day, two digit
    minute of hour, two digit second of minute, and three digit fraction of
    second: `yyyy-MM-dd'T'HH:mm:ss.SSS`.

`date_hour_minute_second_millis` or `strict_date_hour_minute_second_millis`::

    A formatter that combines a full date, two digit hour of day, two digit
    minute of hour, two digit second of minute, and three digit fraction of
    second: `yyyy-MM-dd'T'HH:mm:ss.SSS`.

`date_time` or `strict_date_time`::

    A formatter that combines a full date and time, separated by a 'T':
    `yyyy-MM-dd'T'HH:mm:ss.SSSZZ`.

`date_time_no_millis` or `strict_date_time_no_millis`::

    A formatter that combines a full date and time without millis, separated
    by a 'T': `yyyy-MM-dd'T'HH:mm:ssZZ`.

`hour` or `strict_hour`::

    A formatter for a two digit hour of day: `HH`

`hour_minute` or `strict_hour_minute`::

    A formatter for a two digit hour of day and two digit minute of hour:
    `HH:mm`.

`hour_minute_second` or `strict_hour_minute_second`::

    A formatter for a two digit hour of day, two digit minute of hour, and two
    digit second of minute: `HH:mm:ss`.

`hour_minute_second_fraction` or `strict_hour_minute_second_fraction`::

    A formatter for a two digit hour of day, two digit minute of hour, two
    digit second of minute, and three digit fraction of second: `HH:mm:ss.SSS`.

`hour_minute_second_millis` or `strict_hour_minute_second_millis`::

    A formatter for a two digit hour of day, two digit minute of hour, two
    digit second of minute, and three digit fraction of second: `HH:mm:ss.SSS`.

`ordinal_date` or `strict_ordinal_date`::

    A formatter for a full ordinal date, using a four digit year and three
    digit dayOfYear: `yyyy-DDD`.

`ordinal_date_time` or `strict_ordinal_date_time`::

    A formatter for a full ordinal date and time, using a four digit year and
    three digit dayOfYear: `yyyy-DDD'T'HH:mm:ss.SSSZZ`.

`ordinal_date_time_no_millis` or `strict_ordinal_date_time_no_millis`::

    A formatter for a full ordinal date and time without millis, using a four
    digit year and three digit dayOfYear: `yyyy-DDD'T'HH:mm:ssZZ`.

`time` or `strict_time`::

    A formatter for a two digit hour of day, two digit minute of hour, two
    digit second of minute, three digit fraction of second, and time zone
    offset: `HH:mm:ss.SSSZZ`.

`time_no_millis` or `strict_time_no_millis`::

    A formatter for a two digit hour of day, two digit minute of hour, two
    digit second of minute, and time zone offset: `HH:mm:ssZZ`.

`t_time` or `strict_t_time`::

    A formatter for a two digit hour of day, two digit minute of hour, two
    digit second of minute, three digit fraction of second, and time zone
    offset prefixed by 'T': `'T'HH:mm:ss.SSSZZ`.

`t_time_no_millis` or `strict_t_time_no_millis`::

    A formatter for a two digit hour of day, two digit minute of hour, two
    digit second of minute, and time zone offset prefixed by 'T': `'T'HH:mm:ssZZ`.

`week_date` or `strict_week_date`::

    A formatter for a full date as four digit weekyear, two digit week of
    weekyear, and one digit day of week: `xxxx-'W'ww-e`.

`week_date_time` or `strict_week_date_time`::

    A formatter that combines a full weekyear date and time, separated by a
    'T': `xxxx-'W'ww-e'T'HH:mm:ss.SSSZZ`.

`week_date_time_no_millis` or `strict_week_date_time_no_millis`::

    A formatter that combines a full weekyear date and time without millis,
    separated by a 'T': `xxxx-'W'ww-e'T'HH:mm:ssZZ`.

`weekyear` or `strict_weekyear`::

    A formatter for a four digit weekyear: `xxxx`.

`weekyear_week` or `strict_weekyear_week`::

    A formatter for a four digit weekyear and two digit week of weekyear:
    `xxxx-'W'ww`.

`weekyear_week_day` or `strict_weekyear_week_day`::

    A formatter for a four digit weekyear, two digit week of weekyear, and one
    digit day of week: `xxxx-'W'ww-e`.

`year` or `strict_year`::

    A formatter for a four digit year: `yyyy`.

`year_month` or `strict_year_month`::

    A formatter for a four digit year and two digit month of year: `yyyy-MM`.

`year_month_day` or `strict_year_month_day`::

    A formatter for a four digit year, two digit month of year, and two digit
    day of month: `yyyy-MM-dd`.
