How to make past date unselectable in fullcalendar?

I like this approach:

select: function(start, end) {
    if(start.isBefore(moment())) {
        $('#calendar').fullCalendar('unselect');
        return false;
    }
}

It will essentially disable selection on times before "now".

Unselect method

I have done this in my fullcalendar and it's working perfectly.

you can add this code in your select function.

 select: function(start, end, allDay) {
    var check = $.fullCalendar.formatDate(start,'yyyy-MM-dd');
    var today = $.fullCalendar.formatDate(new Date(),'yyyy-MM-dd');
    if(check < today)
    {
        // Previous Day. show message if you want otherwise do nothing.
        // So it will be unselectable
    }
    else
    {
        // Its a right date
        // Do something
    }
  },

I hope it will help you.

Thanks to this answer, I've found the solution below:

$('#full-calendar').fullCalendar({
    selectable: true,
    selectConstraint: {
        start: $.fullCalendar.moment().subtract(1, 'days'),
        end: $.fullCalendar.moment().startOf('month').add(1, 'month')
    }
});