- var_dump: documentation ( source)
- date_default_timezone_set: documentation ( source)
- date: documentation ( source)
- strtotime: documentation ( source)
<?php
date_default_timezone_set('America/Los_Angeles');
var_dump(strtotime('2013-11-03 01:00:00'));
var_dump(strtotime('2013-11-03 02:00:00'));
var_dump(strtotime('2013-11-03 03:00:00'));
var_dump(strtotime('2013-11-03 03:00:00') - strtotime('2013-11-03 02:00:00'));
var_dump(strtotime('2013-11-03 02:00:00') - strtotime('2013-11-03 01:00:00'));
var_dump(date('Y-m-d H:i:s', strtotime('2013-11-03 00:00:00')));
var_dump(date('Y-m-d H:i:s', strtotime('2013-11-03 01:00:00')));
var_dump(date('Y-m-d H:i:s', strtotime('2013-11-03 02:00:00')));