You are using GetDataTypeName for the dates, so it is showing the correct info. What you want is GetDateTime. More specifically, change the following two lines:
zodjdate.Text = precti.GetDataTypeName(24);
zpridate.Text = precti.GetDataTypeName(23);
to
zodjdate.Text = precti.GetDateTime(24).ToShortDateString();
zpridate.Text = precti.GetDateTime(23).ToShortDateString();