<?php
$date = new DateTime( '2010-03-08 15:48:21' );
$date->setTime( 15, 0, 7 );
$date->setDate( 2008, 07, 22 );
$date->setIsoDate( 2008, 45, 2 );
$date->setTimestamp( 1200128314 );
?>
Result:
2010-03-08T15:48:21+0000
2010-03-08T15:00:07+0000
2008-07-22T15:00:07+0100
2008-11-04T15:00:07+0000
2008-11-15T08:58:34+0000