Manual:Timestamp

The format of timestamps used in MediaWiki URLs and in some of the MediaWiki database fields is yyyymmddhhmmss. For example, the timestamp for August 9th, 2010 00:30:06 UTC is 20100809003006. The timezone for these timestamps is UTC.

MediaWiki's  function provides a convenient way to convert from timestamps in common formats to the MediaWiki timestamp format and vice versa. Read Manual:wfTimestamp for more details. Never use wfTimestamp when inserting a timestamp into the database; this will break in Postgres and possibly other non-MySQL databases. Instead use DatabaseBase::timestamp, aka $dbw->timestamp, which converts a timestamp in one of the formats accepted by wfTimestamp to the format used for inserting into timestamp fields in this DBMS.

is a convenience function that returns a MediaWiki timestamp for the present time.

MediaWiki stores timestamps as strings rather than native timestamp types because MySQL's TIMESTAMP type had major limitations when MediaWiki was first written.

Datatypes
Here are the various timestamp datatypes used in the MediaWiki core: