[PHP] Problem z dodaniem dat Opcje

[o2w5n778]

Witam!
Mam oto taki kod:

[PHP] pobierz, plaintext 
<?php
  $data = date("Y-m-d");;
 
  $dni = 500;
 
  $data =  strtotime($data);
 
  $data = $data + $dni * 24 * 3600;
 
  $data = date('Y-m-d H:i:s',$data);
?>
[PHP] pobierz, plaintext 

Zwraca mi takie błędy:
Warning: date() [function.date]: It is not safe to rely on the system's timezone settings. You are *required* to use the date.timezone setting or the date_default_timezone_set() function. In case you used any of those methods and you are still getting this warning, you most likely misspelled the timezone identifier. We selected 'Europe/Berlin' for 'CET/1.0/no DST' instead in /usr/local/www/apache22/data/register.php on line 52

Warning: strtotime() [function.strtotime]: It is not safe to rely on the system's timezone settings. You are *required* to use the date.timezone setting or the date_default_timezone_set() function. In case you used any of those methods and you are still getting this warning, you most likely misspelled the timezone identifier. We selected 'Europe/Berlin' for 'CET/1.0/no DST' instead in /usr/local/www/apache22/data/register.php on line 56

Warning: date() [function.date]: It is not safe to rely on the system's timezone settings. You are *required* to use the date.timezone setting or the date_default_timezone_set() function. In case you used any of those methods and you are still getting this warning, you most likely misspelled the timezone identifier. We selected 'Europe/Berlin' for 'CET/1.0/no DST' instead in /usr/local/www/apache22/data/register.php on line 60

W czym problem?