p2.js

var d = new Date(2012, 2, 23, 23, 0, 0, 0);
d.setUTCDate(d.getDate() + 3);
console.log(d.toLocaleString());

p2.php

date_default_timezone_set('Europe/Budapest');
echo(
  date(
    "Y-m-d H:i:s",
    mktime(23, 0, 0, 3, 23, 2012)+86400*3
  )
);