Add JavaScript Date Validation into List Item forms

//--验证date有效性，end date必须等于或者大于start date

function PreSaveAction()
{
var date1 = getTagFromIdentifierAndTitle("INPUT","DateTimeFieldDate","Start Date");
var date2 = getTagFromIdentifierAndTitle("INPUT","DateTimeFieldDate","End Date");
var arrDate1 = date1.value.split("/");
var useDate1 = new Date(arrDate1[2], arrDate1[1]-1, arrDate1[0]);
var arrDate2 = date2.value.split("/");
var useDate2 = new Date(arrDate2[2], arrDate2[1]-1, arrDate2[0]);
if(useDate1 > useDate2)
{
alert("The End Date cannot happen earlier than the Start Date");
return false; // Cancel the item save process
}
return true; // OK to proceed with the save item
}


reference: http://edinkapic.blogspot.com/2007/10/add-javascript-date-validation-into.html