function Calendar(element, options, eventSources) {
	var t = this;
	
	
	// exports
	t.options = options;
	t.render = render;
	t.destroy = destroy;
	t.refetchEvents = refetchEvents;
	t.reportEvents = reportEvents;
	t.reportEventChange = reportEventChange;
	t.rerenderEvents = rerenderEvents;
	t.changeView = changeView;
	t.select = select;
	t.unselect = unselect;
	t.prev = prev;
	t.next = next;
	t.prevYear = prevYear;
	t.nextYear = nextYear;
	t.today = today;
	t.gotoDate = gotoDate;
	t.incrementDate = incrementDate;
	t.formatDate = function(format, date) { return formatDate(format, date, options) };
	t.formatDates = function(format, date1, date2) { return formatDates(format, date1, date2, options) };
	t.getDate = getDate;
	t.getView = getView;
	t.option = option;
	t.trigger = trigger;
	
	
	// imports
	EventManager.call(t, options, eventSources);
	var isFetchNeeded = t.isFetchNeeded;
	var fetchEvents = t.fetchEvents;
	
	ResourceManager.call(t, options);
	
	// locals
	var _element = element[0];
	var header;
	var headerElement;
	var content;
	var tm; // for making theme classes
	var currentView;
	var elementOuterWidth;
	var suggestedViewHeight;
	var resizeUID = 0;
	var ignoreWindowResize = 0;
	var date = new Date();
	var events = [];
	var _dragElement;
	
	
	
	/* Main Rendering
	-----------------------------------------------------------------------------*/
	
	
	setYMD(date, options.year, options.month, options.date);
	
	
	function render(inc) {
		if (!content) {
			initialRender();
		}
		else if (elementVisible()) {
			// mainly for the public API
			calcSize();
			_renderView(inc);
		}
	}
	
	
	function initialRender() {
		tm = options.theme ? 'ui' : 'fc';
		element.addClass('fc');
		if (options.isRTL) {
			element.addClass('fc-rtl');
		}
		else {
			element.addClass('fc-ltr');
		}
		if (options.theme) {
			element.addClass('ui-widget');
		}

		content = $("<div class='fc-content' style='position:relative'/>")
			.prependTo(element);

		header = new Header(t, options);
		headerElement = header.render();
		if (headerElement) {
			element.prepend(headerElement);
		}

		changeView(options.defaultView);

		if (options.handleWindowResize) {
			$(window).resize(windowResize);
		}

		// needed for IE in a 0x0 iframe, b/c when it is resized, never triggers a windowResize
		if (!bodyVisible()) {
			lateRender();
		}
	}
	
	
	// called when we know the calendar couldn't be rendered when it was initialized,
	// but we think it's ready now
	function lateRender() {
		setTimeout(function() { // IE7 needs this so dimensions are calculated correctly
			if (!currentView.start && bodyVisible()) { // !currentView.start makes sure this never happens more than once
				renderView();
			}
		},0);
	}
	
	
	function destroy() {

		if (currentView) {
			trigger('viewDestroy', currentView, currentView, currentView.element);
			currentView.triggerEventDestroy();
		}

		$(window).unbind('resize', windowResize);

		header.destroy();
		content.remove();
		element.removeClass('fc fc-rtl ui-widget');
	}
	
	
	function elementVisible() {
		return element.is(':visible');
	}
	
	
	function bodyVisible() {
		return $('body').is(':visible');
	}
	
	
	
	/* View Rendering
	-----------------------------------------------------------------------------*/
	

	function changeView(newViewName) {
		if (!currentView || newViewName != currentView.name) {
			_changeView(newViewName);
		}
	}


	function _changeView(newViewName) {
		ignoreWindowResize++;

		if (currentView) {
			trigger('viewDestroy', currentView, currentView, currentView.element);
			unselect();
			currentView.triggerEventDestroy(); // trigger 'eventDestroy' for each event
			freezeContentHeight();
			currentView.element.remove();
			header.deactivateButton(currentView.name);
		}

		header.activateButton(newViewName);

		currentView = new fcViews[newViewName](
			$("<div class='fc-view fc-view-" + newViewName + "' style='position:relative'/>")
				.appendTo(content),
			t // the calendar object
		);

		renderView();
		unfreezeContentHeight();

		ignoreWindowResize--;
	}


	function renderView(inc) {
		if (
			!currentView.start || // never rendered before
			inc || date < currentView.start || date >= currentView.end // or new date range
		) {
			if (elementVisible()) {
				_renderView(inc);
			}
		}
	}


	function _renderView(inc) { // assumes elementVisible
		ignoreWindowResize++;

		if (currentView.start) { // already been rendered?
			trigger('viewDestroy', currentView, currentView, currentView.element);
			unselect();
			clearEvents();
		}

		freezeContentHeight();
		currentView.render(date, inc || 0); // the view's render method ONLY renders the skeleton, nothing else
		setSize();
		unfreezeContentHeight();
		(currentView.afterRender || noop)();

		updateTitle();
		updateTodayButton();

		trigger('viewRender', currentView, currentView, currentView.element);
		currentView.trigger('viewDisplay', _element); // deprecated

		ignoreWindowResize--;

		getAndRenderEvents();
	}
	
	

	/* Resizing
	-----------------------------------------------------------------------------*/
	
	
	function updateSize() {
		if (elementVisible()) {
			unselect();
			clearEvents();
			calcSize();
			setSize();
			renderEvents();
		}
	}
	
	
	function calcSize() { // assumes elementVisible
		if (options.contentHeight) {
			suggestedViewHeight = options.contentHeight;
		}
		else if (options.height) {
			suggestedViewHeight = options.height - (headerElement ? headerElement.height() : 0) - vsides(content);
		}
		else {
			suggestedViewHeight = Math.round(content.width() / Math.max(options.aspectRatio, .5));
		}
	}
	
	
	function setSize() { // assumes elementVisible

		if (suggestedViewHeight === undefined) {
			calcSize(); // for first time
				// NOTE: we don't want to recalculate on every renderView because
				// it could result in oscillating heights due to scrollbars.
		}

		ignoreWindowResize++;
		currentView.setHeight(suggestedViewHeight);
		currentView.setWidth(content.width());
		ignoreWindowResize--;

		elementOuterWidth = element.outerWidth();
	}
	
	
	function windowResize() {
		if (!ignoreWindowResize) {
			if (currentView.start) { // view has already been rendered
				var uid = ++resizeUID;
				setTimeout(function() { // add a delay
					if (uid == resizeUID && !ignoreWindowResize && elementVisible()) {
						if (elementOuterWidth != (elementOuterWidth = element.outerWidth())) {
							ignoreWindowResize++; // in case the windowResize callback changes the height
							updateSize();
							currentView.trigger('windowResize', _element);
							ignoreWindowResize--;
						}
					}
				}, 200);
			}else{
				// calendar must have been initialized in a 0x0 iframe that has just been resized
				lateRender();
			}
		}
	}
	
	
	
	/* Event Fetching/Rendering
	-----------------------------------------------------------------------------*/
	// TODO: going forward, most of this stuff should be directly handled by the view


	function refetchEvents() { // can be called as an API method
		clearEvents();
		fetchAndRenderEvents();
	}


	function rerenderEvents(modifiedEventID) { // can be called as an API method
		clearEvents();
		renderEvents(modifiedEventID);
	}


	function renderEvents(modifiedEventID) { // TODO: remove modifiedEventID hack
		if (elementVisible()) {
			currentView.setEventData(events); // for View.js, TODO: unify with renderEvents
			currentView.renderEvents(events, modifiedEventID); // actually render the DOM elements
			currentView.trigger('eventAfterAllRender');
		}
	}


	function clearEvents() {
		currentView.triggerEventDestroy(); // trigger 'eventDestroy' for each event
		currentView.clearEvents(); // actually remove the DOM elements
		currentView.clearEventData(); // for View.js, TODO: unify with clearEvents
	}
	

	function getAndRenderEvents() {
		if (!options.lazyFetching || isFetchNeeded(currentView.visStart, currentView.visEnd)) {
			fetchAndRenderEvents();
		}
		else {
			renderEvents();
		}
	}


	function fetchAndRenderEvents() {
		fetchEvents(currentView.visStart, currentView.visEnd);
			// ... will call reportEvents
			// ... which will call renderEvents
	}

	
	// called when event data arrives
	function reportEvents(_events) {
		events = _events;
		renderEvents();
	}


	// called when a single event's data has been changed
	function reportEventChange(eventID) {
		rerenderEvents(eventID);
	}



	/* Header Updating
	-----------------------------------------------------------------------------*/


	function updateTitle() {
		header.updateTitle(currentView.title);
	}


	function updateTodayButton() {
		var today = new Date();
		if (today >= currentView.start && today < currentView.end) {
			header.disableButton('today');
		}
		else {
			header.enableButton('today');
		}
	}
	


	/* Selection
	-----------------------------------------------------------------------------*/
	

	function select(start, end, allDay) {
		currentView.select(start, end, allDay===undefined ? true : allDay);
	}
	

	function unselect() { // safe to be called before renderView
		if (currentView) {
			currentView.unselect();
		}
	}
	
	
	
	/* Date
	-----------------------------------------------------------------------------*/
	
	
	function prev() {
		renderView(-1);
	}
	
	
	function next() {
		renderView(1);
	}
	
	
	function prevYear() {
		addYears(date, -1);
		renderView();
	}
	
	
	function nextYear() {
		addYears(date, 1);
		renderView();
	}
	
	
	function today() {
		date = new Date();
		renderView();
	}
	
	
	function gotoDate(year, month, dateOfMonth) {
		if (year instanceof Date) {
			date = cloneDate(year); // provided 1 argument, a Date
		}else{
			setYMD(date, year, month, dateOfMonth);
		}
		renderView();
	}
	
	
	function incrementDate(years, months, days) {
		if (years !== undefined) {
			addYears(date, years);
		}
		if (months !== undefined) {
			addMonths(date, months);
		}
		if (days !== undefined) {
			addDays(date, days);
		}
		renderView();
	}
	
	
	function getDate() {
		return cloneDate(date);
	}



	/* Height "Freezing"
	-----------------------------------------------------------------------------*/


	function freezeContentHeight() {
		content.css({
			width: '100%',
			height: content.height(),
			overflow: 'hidden'
		});
	}


	function unfreezeContentHeight() {
		content.css({
			width: '',
			height: '',
			overflow: ''
		});
	}
	
	
	
	/* Misc
	-----------------------------------------------------------------------------*/
	
	
	function getView() {
		return currentView;
	}
	
	
	function option(name, value) {
		if (value === undefined) {
			return options[name];
		}
		if (name == 'height' || name == 'contentHeight' || name == 'aspectRatio') {
			options[name] = value;
			updateSize();
		}
	}
	
	
	function trigger(name, thisObj) {
		if (options[name]) {
			return options[name].apply(
				thisObj || _element,
				Array.prototype.slice.call(arguments, 2)
			);
		}
	}
	
	
	
	/* External Dragging
	------------------------------------------------------------------------*/
	
	if (options.droppable) {
		$(document)
			.bind('dragstart', function(ev, ui) {
				var _e = ev.target;
				var e = $(_e);
				if (!e.parents('.fc').length) { // not already inside a calendar
					var accept = options.dropAccept;
					if ($.isFunction(accept) ? accept.call(_e, e) : e.is(accept)) {
						_dragElement = _e;
						currentView.dragStart(_dragElement, ev, ui);
					}
				}
			})
			.bind('dragstop', function(ev, ui) {
				if (_dragElement) {
					currentView.dragStop(_dragElement, ev, ui);
					_dragElement = null;
				}
			});
	}
	

}