function RSRCalendar() {
	// this assumes "monthyear" is id of appropriate text element and
	// boxes have id's 0 through 42, and table has id RSRCalendar
	// yes, that means only one calendar per page
	
	//methods
	this.setMonth = setMonth;
	this.nextMonth = nextMonth;
	this.prevMonth = prevMonth;
	this.nextYear = nextYear;
	this.prevYear = prevYear;
	this.getDate = getDate;
	this.setDate = setDate;
	this.show = show;
	this.hide = hide;

	//this.showMonthYear = showMonthYear; // test purposes only
	
	//instance vars
	this.ref = document.getElementById("RSRCalendar");
	//alert("this.ref is " + this.ref + " with style " + this.ref.style);
	this.y = 2005;
	this.m = 0;
	this.offset = 0;
	this.mLen = 0;
	
	var month = new Array("Jan.", "Feb.", "March", "April", "May", "June", "July", "Aug.", "Sept.", "Oct.", "Nov.", "Dec.");
	var msInDay = 1000 * 60 * 60 * 24;
	var def = "any";

	var d = new Date();
	//alert("In RSRCalendar with date " + d);
	setMonth(d.getFullYear(), d.getMonth()); // current month
	//this.offset = d.getDay();

	function setMonth(year, month) {
		//alert("in setMonth with year " + year + " and month " + month);
		y = year;
		m = month;
		fillCal();
	}
	
	function monthLen() {
		return (new Date(new Date(y, m + 1, 1) - msInDay)).getDate();
	}

	function fillCal() {
		//alert("in filCal with instance data year " + y + " and month " + m);

		var i;
		offset = (new Date(y, m, 1)).getDay();
		mLen = monthLen();
		//alert("offset is " + offset + ", monthLen is " + mLen);
		document.getElementById("monthyear").value = month[m] + " " + y;
		for (i = 0; i < offset; i++) {
			document.getElementById(i).value = "";
		}
		for (i = 0; i < mLen; i++) {
			document.getElementById(i + offset).value = i + 1;
		}
		for (i = mLen + offset; i < 37; i++) {
			document.getElementById(i).value = "";
		}
	}

	function nextMonth() {
		if (m == 11) {
			m = 0;
			y++;
		}
		else
			m++;
		fillCal();
	}
	
	function prevMonth() {
		if (m == 0) {
			m = 11;
			y--;
		}
		else
			m--;
		fillCal();
	}

	function nextYear() {
		y++;
		fillCal();
	}
	
	function prevYear() {
		y--;
		fillCal();
	}

	function z2pad(n) {
		return ("0" + n).substr(-2);
	}
	
	function getDate(id) {
		var dt = id - offset + 1;
		return (dt > 0  &&  dt <= mLen) ? y + "-" + z2pad(m + 1) + "-" + z2pad(dt) : def;
	}
	
	function setDate(textDate) {
		if(textDate == def) { // if none set, use current
			var d = new Date();
			setMonth(d.getFullYear(), d.getMonth()); // current month
		}
		else // assume format yyyy-mm-dd
			setMonth(parseInt(textDate.substr(0, 4)), parseInt(textDate.substr(5, 2)) - 1);
	}
	
	function show() {
		this.ref.style.visibility = "visible";
	}

	function hide() {
		this.ref.style.visibility = "hidden";
	}

	/*
	function showMonthYear() {
		alert("In showMonthYear: " + m + " " + y);
	}
	*/
}