How to strip date from time

$("#popupEventForm").find("form").find("#eventDate").val(calEvent.start).toString("MM/dd/yy");

public JsonResult GetDiarySummary(double start, double end, string Title)
        {
            var ApptListForDate = DiaryEvent.LoadAppointmentSummaryInDateRange(start, end, Title);
            var eventList = from e in ApptListForDate
                            select new
                            {
                                id = e.ID,
                                title = e.Title,
                                appointmentLength = e.AppointmentLength,
                                start = e.StartDateString.FormatWith("MM/dd/yy"),
                                scheduledTime = e.StartDateString,
                                end = e.EndDateString,
                                someKey = e.SomeImportantKeyID,
                                allDay = false
                            };
            var rows = eventList.ToArray();
            return Json(rows, JsonRequestBehavior.AllowGet);
        }