Get the number of seconds since Jan 1, 0001 in PHP

seconds_since.php

<?php

    /*
     * Very simple way to get the number of seconds from Jan 1, 0001 or any other date
     * the normal date/time functions only work from 1 Jan 1970
     * Requires PHP 5.3 or above
     * Start: must be in YYYY-MM-DD format
     * End: must be in YYYY-MM-DD format
     */

    function seconds_since($start='0001-01-01',$end=date(Y-m-d))
    (
        
        $datetime1 = new DateTime($start);
        $datetime2 = new DateTime($end);
        $interval = $datetime1->diff($datetime2);
    
        return $interval->format('%a') * 24 * 60 * 60;
    }

?>