Aqui tienes el codigo:
Código PHP:
<?
function add_zero($a){
$b = $a;
if(strlen($a) == 1){
$b = "0".$a;
}
return $b;
}
function day_th($gmt, $no=30){
// default $no = 30 later
// get GMT datetime as standard for 'now()'
// $gmt = gmstrftime("%Y-%m-%d %H:%M:%S");
$d = explode(" ",$gmt);
$date = $d[0];
$time = $d[1];
$date_x = explode("-",$date);
$year = $date_x[0];
$month = $date_x[1];
$day = $date_x[2];
$time_x = explode(":",$time);
$hour = $time_x[0];
$minute = $time_x[1];
$second = $time_x[2];
// create UNIX TIMESTAMP of the GMT above
$t = mktime($hour, $minute, $second, $month, $day, $year);
// 1 h = 3600 sec
// 1 d = 24 h
// 1 d = 86400 sec
// 30 d = 2592000 sec
$unix_stamp = 86400 * $no;
$res = getdate($t + $unix_stamp);
$ris = array_values($res);
list($seconds,$minutes,$hours,$mday,$wday,$mon,$year,
$yday,$weekday,$month,$unix) = $ris;
$mon = add_zero($mon);
$mday = add_zero($mday);
$seconds = add_zero($seconds);
$minutes = add_zero($minutes);
$hours = add_zero($hours);
$day_th = $year."-".$mon."-".$mday." ".$hours.":".$minutes.":".$seconds;
return $day_th;
}
// $gmt = gmstrftime("%Y-%m-%d %H:%M:%S");
$gmt = "2005-02-28 00:00:01";
$nextdate = day_th($gmt, $no=1);
echo $gmt."<br>".$nextdate."<br>";
?>
Espero que te sirva
Un Saludo!