Bill,
I know this question is pretty much ancient, but I needed a solution and figured I’d post it here for others. I solved the problem myself by attaching the viewDisplay event to my calendar (this event was removed in v2 of FullCalendar, viewRender may be used instead).
$("#calendar").fullCalendar({
viewDisplay: function (element) {
}
});
Once you have access to the element parameter, you can get the date by using element.start or element.visStart. If you’re in the month view, start will provide you with the first day of the month that you’re viewing, visStart will give you the first visible day of the month