JSON Date parameter passed to MVC Action is always null

Microsoft use JavaScriptSerializer to serialize/desirealize the ASP.NET MVC data. If use /Date(utcDate)/ format for the Date data type. Try to use

'"\\/Date(' + myStory.Deadline.getTime() + ')\\/"'

or

var d = myStory.Deadline;var dateForMS = '"\\/Date(' +        Date.UTC (d.getUTCFullYear(), d.getUTCMonth(),                  d.getUTCDate(), d.getUTCHours(),                  d.getUTCMinutes(), d.getUTCSeconds(),                  d.getUTCMilliseconds()) + ')\\/"'

You can also just use Sys.Serialization.JavaScriptSerializer from MicrosoftAjax.js to serialize Deadline or any other Date type.

UPDATED: Probably you should use '\/Date(' and ')\/' instead of '"\\/Date(' and ')\\/"'. All depends on where you will insert the string.

UPDATED 2: Now I have it! ASP.NET MVC is used mostly for the posting Form fields per Ajax. On the server side will be just used Parse method for every type to convert the posted parameter to the type. So one can use any string format which are supported by DateTime.Parse. For example you can use ISO 8601 format like '2010-08-29T13:15:00.0000000Z'. To do this in modern browsers (firefox, chrome) one can use toISOString() function. To be more independend one can implement data conversion like described in http://williamsportwebdeveloper.com/cgi/wp/?p=503:

var d = new Date($('#story-deadline').val())//var d = new Date(); // get the date. Here we use just Now.var dAsISOString;if ($.isFunction(d.toISOString)) {    //alert("internal toISOString are used!");    dAsISOString = d.toISOString();}else {    dAsISOString = d.getUTCFullYear() + '-' + padzero(d.getUTCMonth() + 1) + '-' +                   padzero(d.getUTCDate()) + 'T' + padzero(d.getUTCHours()) + ':' +                   padzero(d.getUTCMinutes()) + ':' + padzero(d.getUTCSeconds())+'.'+                   pad2zeros(d.getUTCMilliseconds()) + 'Z';}var myStory = { Summary: 'Test description', Size: 8, Dedline: dAsISOString };$.ajax({    url: '/Project/1/AddStory',    data: { Summary: myStory.Summary, Size: myStory.Size, Dedline: myStory.Dedline },    dataType: 'json',    // ...});