I’m using the plug in FullCalendar in a month view (default one),
And when the month is printed it’s showing one more week each time.
Let me know if you want more details or screenshots
$('#calendar_expanded').fullCalendar({
defaultView: "month",
firstDay: $('#inputUserStartWeek').val(),
height: $(window).height()-100
});

Try setting weekMode to liquid or variable:
http://arshaw.com/fullcalendar/docs/display/weekMode/