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]="Sunday";
weekday[2]="Monday";
weekday[3]="Tuesday";
weekday[4]="Wednesday";
weekday[5]="Thursday";
weekday[6]="Friday";
weekday[7]="Saturday";
if (day != date) alert("Sorry!  That appears to be an invalid date!"+day+" ..."+date+"::"+oyear+"..."+year+" "+dob+"=="+wyear+".-.-"+thenx+" "+day+" "+month);
else {
dayborn = weekday[theday];
dob = dayborn + ", " + month + " " + date + ", " + oyear + ".";
alert("You were born on " + dob);
   }
}