function y2kComplaint(year) { return (year < 1000)? year + 1900: year; }

function isDate (dayParam, monthParam, yearParam) {
	
	var day = Number(dayParam); var month = Number(monthParam); var year = Number(yearParam);
	var today = new Date();

	year = ((!year)? y2kComplaint(today.getYear()): year);
	month = ((!month)? today.getMonth(): month-1);
	if (!day) return false;

	var testDate = new Date(year, month, day);

	if ((y2kComplaint(testDate.getYear()) == year) && (month == testDate.getMonth()) && (day == testDate.getDate())) return true;
	else return false;
}