function cal(year, month, day) {
	today = new Date();
	if (!year) var year = today.getFullYear();
	if (!month) var month = today.getMonth();
	else month--;
	if (!day) var day = today.getDate();
	var leap_year = false;
	if ((year % 4 == 0 && year % 100 != 0) || (year % 400 == 0)) leap_year = true;
	lom = new Array(31, 28 + leap_year, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31);
	dow = new Array("日", "月", "火", "水", "木", "金", "土");
	var days = 0;
	for (var i = 0; i < month; i++) days += lom[i];
	var week = Math.floor((year * 365.2425 + days) % 7);
	var j = 0;
	var when = year + "年 " + (month + 1) + "月";
	var calendar = "<table summary=\"" + when + "のカレンダー\">\n";
	calendar += "<caption>" + when + "<\/caption>\n<tr>";
	for (i = 0; i < 7; i++) {
		calendar += "<td";
		if (i == 0) calendar += " class=\"sunday\"";
		if (i == 6) calendar += " class=\"saturday\"";
		calendar += ">" + dow[i] + "<\/td>";
	}
	calendar += "<\/tr>\n<tr>";
	for (i = 0; i < week; i++, j++) calendar += "<td><\/td>";
	for (i = 1; i <= lom[month]; i++) {
		calendar += "<td";
		calendar += " class=\"";
		if (day == i) calendar += " today";
		if (j == 0) calendar += " sunday";
		if (j == 6) calendar += " saturday";
		calendar += "\"";
		calendar += ">" + i + "<\/td>";
		j++;
		if (j > 6) {
			calendar += "<\/tr>\n<tr>";
			j = 0;
		}
	}
	for (i = j; i > 6; i++) calendar += "<td><\/td>";
	calendar += "<\/tr>\n<\/table>\n";
	return calendar;
}