function calculate() {
month = document.form.month.selectedIndex;
month = document.form.month.options[month].value;
day = document.form.day.selectedIndex;
day = document.form.day.options[day].value;
year = document.form.year.value;

var oyear=year

var dob = " "+ year +", "+month + ",  "+day;
var thenx = new Date(dob);

var year=thenx.getYear();
if (year<100) year="19" + thenx.getYear();
else year=thenx.getYear();

if (year > 1969) wyear=year;
else {
if (oyear<1900) {
if (oyear>1800) {
wrelyear= (eval(oyear)-1801)%(28);
wyear = wrelyear+1981;
}
else wyear = 1970
}
else
if (oyear>1900) {wrelyear= (eval(oyear)-1901)%(28);
wyear= wrelyear+1985
}
else
if (oyear==1900) {wyear= 1990;
   }
}
var dob = " "+ wyear +", "+month + ",  "+day;
var thenx = new Date(dob);

var theday = thenx.getDay()+1;
var date=thenx.getDate();

var weekday = new Array(6);
weekday[1]="Sonntag";
weekday[2]="Montag";
weekday[3]="Dienstag";
weekday[4]="Mittwoch";
weekday[5]="Donnerstag";
weekday[6]="Freitag";
weekday[7]="Samstag";
if (day != date) alert("Sorry!  Das scheint nicht richtig zu sein!"+day+" ..."+date+"::"+oyear+"..."+year+" "+dob+"=="+wyear+".-.-"+thenx+" "+day+" "+month);
else {
dayborn = weekday[theday];
dob = dayborn + ", " + month + " " + date + ", " + oyear + ".";
alert("Dein Geburtstag war an einem " + dob);
   }
}