Parsing strings for date time information with the strtotime() function:
<?php
$ts = strtotime("2005-07-11 22:16:50 CEST");
?>
With initial timestamp:
<?php
$date = strtotime("2005-07-11 22:16:50 CEST");
$ts = strtotime("next week", $date);
?>
The timestamp's range is still limited to what the CPU supports.