- var_dump: documentation ( source)
- strtotime: documentation ( source)
- gmdate: documentation ( source)
<?php
var_dump(gmdate('Y-m-d', 1399669200000 /1000 ));
var_dump(gmdate('Y-m-d', 1399755600000 /1000 ));
var_dump(strtotime('2014-05-10 23:00:00'));
var_dump(gmdate('Y-m-d', 1400878800000/1000 ));