fullCalendar multi-day event spans 1 day too short

I know this is old but it still gets a lot of views and is high up on web searches. so please see detailed answer here of my solution FullCalendar end date is not inclusive

There is no fullDayThreshold, I think you are referring to nextDayThreshold, check documentation here:

http://fullcalendar.io/docs/event_rendering/nextDayThreshold/

That should do it. Regards.

Edit: You should add time to your dates for that option to work. Example:

            {
                'title':'test2',
                'start':'2014-09-17T00:00:00',
                'end':'2014-09-18T01:00:00'
            },

Using parameter
nextDayThreshold: "00:00:00",

Try using nextDayThreshold parameter:

$('#calendar').fullCalendar({
     **nextDayThreshold**: '00:00:00', // 9am

nextDayThreshold set the minimum time it must be in order for it to render as if it were on that day.