When i pass data: as datetime; controller return me null value

Hi All,

Before i pass into controller, the date having value. But when go into controller, the date become null:

"data3": data.start_date, "data4": data.end_date

Both also having value in datetime format: Mon Jul 22 00:00:00 UTC+0800 2013

var msg=false;
                                 $.ajax({
                                     type: "POST",
                                     async: false,
                                     url: "<%=Url.Content("~/Calendar/getValbyID/")%>",
                                     data: { "data1":data.leavetype_id, "data2":'<%=Session["LegalEntity"]%>', "data3": data.start_date, "data4": data.end_date },

Please advise.

Thank you.

Regards,

Micheale