i solved my problem and all is working fine now.
i hope that this will help some people.
also first i had it like this:
// months must be -1 !!! because it counts from 0 to 11 and not from 1 to 12
var utcdate = new Date.UTC(2011,2,15);
and it didn't work because of the "new" before Date.UTC which i didn't knew that it shouldn't be there, because it has to be if you use only Date and not Date.UTC
and now it's working perfect like this:
var utcdate = Date.UTC(2011,2,15);
and you get the time / date in miliseconds i think... you have to divide the time you get with 1000 to get seconds. and then with 60 to get minutes and then with 60 once more to get hours and then with 24 to get days, etc. ...