getNumberOfTripDays: function() {
    var startDate = this.$form.find('#qq-form-start-date').datepicker('getDate');
    var endDate = this.$form.find('#qq-form-end-date').datepicker('getDate');
    var _numOfTripDays = '';

    if (startDate && endDate) {
        // Discard the time and time-zone information.
        var MS_PER_DAY = 1000 * 60 * 60 * 24;
        var utc1 = Date.UTC(startDate.getFullYear(), startDate.getMonth(), startDate.getDate());
        var utc2 = Date.UTC(endDate.getFullYear(), endDate.getMonth(), endDate.getDate());
        var diffDays = Math.floor((utc2 - utc1) / _MS_PER_DAY);

        // dates are inclusive so add 1
        _numOfTripDays = diffDays + 1

        return _numOfTripDays;
    }

    return _numOfTripDays;
},