gistfile1

var DatePicker=Class.create({
	_monthNames:['January','February','March','April','May','June','July','August','September','October','November','December'],
	initialize:function() {
		this._date=new Date();
		this._userCallback=false;
		
		this._monthRow=new Element('tr');
		this._monthRow.insert(new Element('td',{style:'cursor:pointer;'}));
		this._monthRow.insert(new Element('td',{colspan:5,style:'text-align:center;'}));
		this._monthRow.insert(new Element('td',{style:'text-align:right; cursor:pointer;'}));
		this._monthRow.select('td')[0].appendChild(document.createTextNode('<'));
		this._monthRow.select('td')[1].appendChild(document.createTextNode(this._monthNames[this._date.getMonth()]));
		this._monthRow.select('td')[2].appendChild(document.createTextNode('>'));
		
		this._yearRow=new Element('tr');
		this._yearRow.insert(new Element('td',{style:'cursor:pointer;'}));
		this._yearRow.insert(new Element('td',{colspan:5,style:'text-align:center;'}));
		this._yearRow.insert(new Element('td',{style:'text-align:right; cursor:pointer;'}));
		this._yearRow.select('td')[0].appendChild(document.createTextNode('<'));
		this._yearRow.select('td')[1].appendChild(document.createTextNode(this._date.getFullYear().toPaddedString(0)));
		this._yearRow.select('td')[2].appendChild(document.createTextNode('>'));
		
		this._pickerTable=new Element('table');
		this._pickerTable.insert(new Element('tbody'));
		this._pickerTable.down().insert(this._monthRow);
		this._pickerTable.down().insert(new Element('tr'));
		['S','M','T','W','T','F','S'].each(function(it) {
			var newCell=new Element('td',{style:'text-align:center;'});
			newCell.appendChild(document.createTextNode(it));
			this._pickerTable.select('tr')[1].insert(newCell);
		},this);
		this._pickerTable.down().insert(new Element('tr'));
		$R(1,7).each(function() {
			var newCell=new Element('td',{style:'text-align:center;'});
			newCell.appendChild(document.createTextNode('\xa0'));
			this._pickerTable.select('tr')[2].insert(newCell);
		},this);
		$R(1,5).each(function() {
			this._pickerTable.down().insert(this._pickerTable.select('tr')[2].clone(true));
		},this);
		this._pickerTable.down().insert(this._yearRow);
		
		this._updateTable();
	},
	_daysInMonth:function() {
		if (this._date.getMonth() == 0 || this._date.getMonth() == 2 || this._date.getMonth() == 4 || this._date.getMonth() == 6 || this._date.getMonth() == 7 || this._date.getMonth() == 9 || this._date.getMonth() == 11) {
			return 31;
		}
		else if (this._date.getMonth() == 3 || this._date.getMonth() == 5 || this._date.getMonth() == 8 || this._date.getMonth() == 10) {
			return 30;
		}
		else if (this._date.getMonth() == 1) {
			if (new Date(this._date.getFullYear(),1,29).getDate() == 29) {
				return 29;
			}
			else {
				return 28;
			}
		}
	},
	_updateTable:function() {
		if (this._userCallback) {
			this._userCallback(this._date);
		}
		
		if (this._pickerTable.select('.highlighted')[0]) {
		  this._pickerTable.select('.highlighted')[0].removeClassName('highlighted');
		}
		
		this._monthRow.select('td')[1].replaceChild(document.createTextNode(this._monthNames[this._date.getMonth()]),this._monthRow.select('td')[1].firstChild);
		this._yearRow.select('td')[1].replaceChild(document.createTextNode(this._date.getFullYear().toPaddedString(0)),this._yearRow.select('td')[1].firstChild);
		
		$R(0,(new Date(this._date.getFullYear(),this._date.getMonth(),1)).getDay()-1).each(function(it) {
			this._pickerTable.select('tr')[2].select('td')[it].replaceChild(document.createTextNode('\xa0'),this._pickerTable.select('tr')[2].select('td')[it].firstChild);
			this._pickerTable.select('tr')[2].select('td')[it].setStyle({cursor:'auto'});
		},this);
		
		var col=(new Date(this._date.getFullYear(),this._date.getMonth(),1)).getDay();
		var row=2;
		var day=1;
		while (day <= this._daysInMonth()) {
			this._pickerTable.select('tr')[row].select('td')[col].replaceChild(document.createTextNode(day.toPaddedString(0)),this._pickerTable.select('tr')[row].select('td')[col].firstChild);
			this._pickerTable.select('tr')[row].select('td')[col].setStyle({cursor:'pointer'});
			if (day == this._date.getDate()) {
				this._pickerTable.select('tr')[row].select('td')[col].addClassName('highlighted');
			}
			col++;
			if (col == 7) {
				col=0;
				row++;
			}
			day++;
		}
		
		while (row < 8 && col < 7) {
			this._pickerTable.select('tr')[row].select('td')[col].replaceChild(document.createTextNode('\xa0'),this._pickerTable.select('tr')[row].select('td')[col].firstChild);
			this._pickerTable.select('tr')[row].select('td')[col].setStyle({cursor:'auto'});
			col++;
			if (col == 7) {
				col=0;
				row++;
			}
		}
	},
	_prevYear:function() {
		this._date.setFullYear(this._date.getFullYear()-1);
		this._updateTable();
	},
	_nextYear:function() {
		this._date.setFullYear(this._date.getFullYear()+1);
		this._updateTable();
	},
	_prevMonth:function() {
		this._date.setMonth(this._date.getMonth()-1);
		this._updateTable();
	},
	_nextMonth:function() {
		this._date.setMonth(this._date.getMonth()+1);
		this._updateTable();
	},
	_thisDay:function(instance) {
		if (this.firstChild.nodeValue != '\xa0') {
			instance._date.setDate(this.firstChild.nodeValue);
			instance._updateTable();
		}
	},
	beInserted:function(targetElement) {
		$(targetElement).insert(this._pickerTable);
		Event.observe(this._pickerTable.select('tr')[0].select('td')[0],'click',this._prevMonth.bind(this));
		Event.observe(this._pickerTable.select('tr')[0].select('td')[2],'click',this._nextMonth.bind(this));
		Event.observe(this._pickerTable.select('tr')[8].select('td')[0],'click',this._prevYear.bind(this));
		Event.observe(this._pickerTable.select('tr')[8].select('td')[2],'click',this._nextYear.bind(this));
		$R(2,7).each(function(row) {
			$R(0,6).each(function(col) {
				Event.observe(this._pickerTable.select('tr')[row].select('td')[col],'click',this._thisDay.curry(this));
			},this);
		},this);
		return this._pickerTable;
	},
	changeCallback:function(callback) {
		this._userCallback=callback;
		this._userCallback(this._date);
	}
});