Date difference in Javascript (ignoring time of day)

Question

I\'m writing an equipment rental application where clients are charged a fee for renting equipment based on the duration (in days) of the rental. So, basically, (daily fee *

Answer 1

Need date.js, http://code.google.com/p/datejs/

function CalculateDuration(startDate, endDate) {

var sdt = Date.parse(startDate);
var edt = Date.parse(endDate);

var sdtYear = sdt.getYear();
var edtYear = edt.getYear();
var sdtMonth = sdt.getMonth();
var edtMonth = edt.getMonth();
var sdtDay = sdt.getDate();
var edtDay = edt.getDate();

var StartDateMonthDays = Date.getDaysInMonth(sdtYear, sdtMonth);
var EndDateMonthDays = Date.getDaysInMonth(edtYear, edtMonth);

if (edtMonth < sdtMonth) { //Means the ending month is earlier, which invalidates the operation

    alert("Ending month cannot be earlier than the starting month")

}

//Months are equal, if month is the next month of the start date month, 
//the operation fails, thus we need to calculate month difference first
else if (edtMonth > sdtMonth) {

    //Need to count how many days are left to finish the month
    var daysToMonthFinish = StartDateMonthDays - sdtDay;
    var calculatedDuration = daysToMonthFinish + edtDay;
    $("#hdn_duration").val(calculatedDuration);

}
//If months are the same, it is safe to just calculate the end day minus the start day
else {

    var calcDuration = edtDay - sdtDay;
    $("#hdn_duration").val(calcDuration);
}