jQuery UI Datepicker with dependencies on dates.

datepicker.js

// Inputs must be in the same <form>
// This is not Tested, if there are error comment please
var selectorFromInput = '.arrival';
var selectorToInput = '.departure';
var addDays = 7;
$( selectorFromInput + ", " + selectorToInput).datepicker({
    minDate:0,
    firstDay:1,
    onSelect:function (dateText, inst) {
        if($(this).hasClass(selectorFromInput.replace('.', ''))) {
            var quickfinderform = $(this).parents('form:first');
            if(quickfinderform) {
                if ($(this).hasClass(selectorFromInput.replace('.', ''))) {
                    var nextdate = $("input"+selectorToInput, quickfinderform);

                    var currdate = $(this).datepicker("getDate");
                    var dateTime = $(this).datepicker("getDate");

                    var departureDate = quickfinderform.find('input'+selectorToInput).datepicker('getDate');
                    nextdate.datepicker("option", "minDate", dateTime );
                    if( currdate >= departureDate ){
                        currdate.setDate(currdate.getDate() + addDays);
                        nextdate.datepicker("setDate", currdate);
                    }

                }
            }
        }
        $(this).trigger('change');
    }
});