In case anybody runs into this common scenario, here is the fix...
[Controller]
[HttpPost]
public ActionResult Index(EditorValidation e)
{
ViewBag.Message = 'Welcome to ASP.NET MVC!';
DatePickerModel model = new DatePickerModel();
model.DisplayDefaultDateOnLoad =
true;
ViewData["datemodel"] = model;
return View();
}
[View]
@Html.Syncfusion().DatePickerFor(model
=> model.DateTimeValue, (DatePickerModel)ViewData["datemodel"])