Implementation of disabled elements for foundation datepicker project https://github.com/najlepsiwebdesigner/foundation-datepicker/

foundation-datepicker-disabled.js

// implementation of disabled form fields
var nowTemp = new Date();
var now = new Date(nowTemp.getFullYear(), nowTemp.getMonth(), nowTemp.getDate(), 0, 0, 0, 0);
var checkin = $('#dpd1').fdatepicker({
	onRender: function (date) {
		return date.valueOf() < now.valueOf() ? 'disabled' : '';
	}
}).on('changeDate', function (ev) {
	if (ev.date.valueOf() > checkout.date.valueOf()) {
		var newDate = new Date(ev.date)
		newDate.setDate(newDate.getDate() + 1);
		checkout.update(newDate);
	}
	checkin.hide();
	$('#dpd2')[0].focus();
}).data('datepicker');
var checkout = $('#dpd2').fdatepicker({
	onRender: function (date) {
		return date.valueOf() <= checkin.date.valueOf() ? 'disabled' : '';
	}
}).on('changeDate', function (ev) {
	checkout.hide();
}).data('datepicker');

Change this:
if (ev.date.valueOf() > checkout.date.valueOf()) {
var newDate = new Date(ev.date)
newDate.setDate(newDate.getDate() + 1);
checkout.update(newDate);
}
checkin.hide();

To this:
if(ev.date){
if (ev.date.valueOf() > checkout.date.valueOf()) {
var newDate = new Date(ev.date)
newDate.setDate(newDate.getDate() + 1);
checkout.update(newDate);
checkin.hide();
}
}

https://gist.github.com/onionstand/b006d424c220c412c7c6fae809d2f67a