<?php
$selectedTime = '2013-09-29 01:50:00';
$datetime = DateTime::createFromFormat('Y-m-d g:i:s', $selectedTime, new DateTimeZone('Pacific/Auckland'));
$dt = $datetime->modify('+15 minutes');
echo $datetime->format('g:i:s');
PD9waHAKCiRzZWxlY3RlZFRpbWUgPSAnMjAxMy0wOS0yOSAwMTo1MDowMCc7CiRkYXRldGltZSA9IERhdGVUaW1lOjpjcmVhdGVGcm9tRm9ybWF0KCdZLW0tZCBnOmk6cycsICRzZWxlY3RlZFRpbWUsIG5ldyBEYXRlVGltZVpvbmUoJ1BhY2lmaWMvQXVja2xhbmQnKSk7CiRkdCA9ICRkYXRldGltZS0+bW9kaWZ5KCcrMTUgbWludXRlcycpOwplY2hvICRkYXRldGltZS0+Zm9ybWF0KCdnOmk6cycpOw==