I think the most logical answer in this regard is to set the system clock to the relevant feature.
[HttpPost]
public ActionResult Yeni(tblKategori kategori)
{
kategori.CREATEDDATE = DateTime.Now;
var ctx = new MvcDbStokEntities();
ctx.tblKategori.Add(kategori);
ctx.SaveChanges();
return RedirectToAction("Index");//listele sayfasina yönlendir.
}