&reftitle.constants;

The `DATE_`*`` constants are defined and offer standard date representations, which can be used along with the date format functions (like `date`).

# Available returnFormat for date_sunrise and date_sunset

These constants are deprecated as of PHP 8.4.0. The corresponding `date_sunrise` and `date_sunset` functions are deprecated as of PHP 8.1.0.

`SUNFUNCS_RET_TIMESTAMP` (`int`)

- Timestamp

`SUNFUNCS_RET_STRING` (`int`)

- Hours:minutes (example: `08:02`)

`SUNFUNCS_RET_DOUBLE` (`int`)

- Hours as floating point number (example `8.75`)

## `DATE_`*`` constants

`DATE_ATOM` (`string`)

- Atom (example: `2005-08-15T15:52:01+00:00`)

`DATE_COOKIE` (`string`)

- HTTP Cookies (example: `Monday, 15-Aug-2005 15:52:01 UTC`)

`DATE_ISO8601` (`string`)

- ISO-8601 (example: `2005-08-15T15:52:01+0000`)

  This format is not compatible with ISO-8601, but is left this way for backward compatibility reasons. Use `DATE_ISO8601_EXPANDED`, `DATE_ATOM` for compatibility with ISO-8601 instead (ref ISO8601:2004 section 4.3.3 clause d).

`DATE_ISO8601_EXPANDED` (`string`)

- ISO-8601 Expanded (example: `+10191-07-26T08:59:52+01:00`)

  This format allows for year ranges outside of ISO-8601's normal range of `0000`-`9999` by always including a sign character. It also ensures that the timezone part (`+01:00`) is compatible with ISO-8601.

`DATE_RFC822` (`string`)

- RFC 822 (example: `Mon, 15 Aug 05 15:52:01 +0000`)

`DATE_RFC850` (`string`)

- RFC 850 (example: `Monday, 15-Aug-05 15:52:01 UTC`)

`DATE_RFC1036` (`string`)

- RFC 1036 (example: `Mon, 15 Aug 05 15:52:01 +0000`)

`DATE_RFC1123` (`string`)

- RFC 1123 (example: `Mon, 15 Aug 2005 15:52:01 +0000`)

`DATE_RFC7231` (`string`)

- RFC 7231 (as of PHP 7.0.19 and 7.1.5) (example: `Sat, 30 Apr 2016 17:52:13 GMT`)

`DATE_RFC2822` (`string`)

- RFC 2822 (example: `Mon, 15 Aug 2005 15:52:01 +0000`)

`DATE_RFC3339` (`string`)

- Same as `DATE_ATOM`.

`DATE_RFC3339_EXTENDED` (`string`)

- RFC 3339 EXTENDED format (example: `2005-08-15T15:52:01.000+00:00`)

`DATE_RSS` (`string`)

- RSS (example: `Mon, 15 Aug 2005 15:52:01 +0000`). &Alias; `DATE_RFC1123`.

`DATE_W3C` (`string`)

- World Wide Web Consortium (example: `2005-08-15T15:52:01+00:00`). &Alias; `DATE_RFC3339`.