- date: documentation ( source)
- strtotime: documentation ( source)
<?php
$date = new DateTime('@0', new DateTimeZone('UTC'));
$A = $date->format('Y-m-d H:i:s');
$date->modify("+64 minutes");
$B = $date->format('Y-m-d H:i:s');
echo date('h:i', strtotime($B) - strtotime($A));