<!--

function cala_day(form) {
	
	var nDay =  parseInt(form.day.options[form.day.selectedIndex].value);
	var nMonth = parseInt(form.month.options[form.month.selectedIndex].value);
	var nYear =  parseInt(form.year.value);

	var nDayOfWeek = cala_weekday(nDay, nMonth, nYear)
	
	day_display(form, nDayOfWeek)
}

function cala_weekday( x_nDay, x_nMonth, x_nYear) {

	if(x_nMonth >= 3){	
		x_nMonth -= 2;
	}
	else {
		x_nMonth += 10;
	}

	if( (x_nMonth == 11) || (x_nMonth == 12) ){
		x_nYear--;
	}

	var nCentNum = parseInt(x_nYear / 100);
	var nDYearNum = x_nYear % 100;

	var g = parseInt(2.6 * x_nMonth - .2);

	g +=  parseInt(x_nDay + nDYearNum);
	g += nDYearNum / 4;	
	g = parseInt(g);
	g += parseInt(nCentNum / 4);
	g -= parseInt(2 * nCentNum);
	g %= 7;
	
	if(x_nYear >= 1700 && x_nYear <= 1751) {
		g -= 3;
	}
	else {
		if(x_nYear <= 1699) {
			g -= 4;
		}
	}
	
	if(g < 0){
		g += 7;
	}
	
	return g;
}

function day_display(form, x_nDayOfWeek) {

	if(x_nDayOfWeek == 0) {
		form.birthday.value = "Zondag";
		return;
	}
	if(x_nDayOfWeek == 1) {
		form.birthday.value = "Maandag";
		return;
	}
	if(x_nDayOfWeek == 2) {
		form.birthday.value = "Dinsdag";
		return;
	}
	if(x_nDayOfWeek == 3) {
		form.birthday.value = "Woensdag";
		return;
	}
	if(x_nDayOfWeek == 4) {
		form.birthday.value = "Donderdag";
		return;
	}
	if(x_nDayOfWeek == 5) {
		form.birthday.value = "Vrijdag";
		return;
	}
	if(x_nDayOfWeek == 6) {
		form.birthday.value = "Zaterdag";
		return;
	}

	form.birthday.value = "Fout, 'Jaar'.";
}
//-->