Validate that end date is greater than start date with jQuery

Little late to the party but here is my part

Date.parse(fromDate) > Date.parse(toDate)

Here is the detail:

var from = $("#from").val();
var to = $("#to").val();

if(Date.parse(from) > Date.parse(to)){
   alert("Invalid Date Range");
}
else{
   alert("Valid date Range");
}

Just expanding off fusions answer. this extension method works using the jQuery validate plugin. It will validate dates and numbers

jQuery.validator.addMethod("greaterThan", 
function(value, element, params) {

    if (!/Invalid|NaN/.test(new Date(value))) {
        return new Date(value) > new Date($(params).val());
    }

    return isNaN(value) && isNaN($(params).val()) 
        || (Number(value) > Number($(params).val())); 
},'Must be greater than {0}.');

To use it:

$("#EndDate").rules('add', { greaterThan: "#StartDate" });

or

$("form").validate({
    rules: {
        EndDate: { greaterThan: "#StartDate" }
    }
});

var startDate = new Date($('#startDate').val());
var endDate = new Date($('#endDate').val());

if (startDate < endDate){
// Do something
}

That should do it I think

Reference jquery.validate.js and jquery-1.2.6.js. Add a startDate class to your start date textbox. Add an endDate class to your end date textbox.

Add this script block to your page:-

<script type="text/javascript">
    $(document).ready(function() {
        $.validator.addMethod("endDate", function(value, element) {
            var startDate = $('.startDate').val();
            return Date.parse(startDate) <= Date.parse(value) || value == "";
        }, "* End date must be after start date");
        $('#formId').validate();
    });
</script>

Hope this helps :-)