SqlDateTime overflow error in asp.net

Question

I want to insert the (Day,Date,Time) from a Calendar and TimePicker a in my DB but I got this error

"SqlDateTime overflow"

Date access code:

 public void InsertExam(SqlCommand cmd)
    {
        con.Open();
        cmd.Connection = con;
        cmd.CommandText = "InsertExam";
        cmd.CommandType = CommandType.StoredProcedure;
        cmd.ExecuteNonQuery();
        con.Close();

    }

Business

 public void InsertExam_record()
        {

            cmd.Parameters.AddWithValue("@EWeekday", EWeekday);
            cmd.Parameters.AddWithValue("@BegainTime", BegainTime);
            cmd.Parameters.AddWithValue("@EndTime", EndTime);
            cmd.Parameters.AddWithValue("@Duration", Duration);
            cmd.Parameters.AddWithValue("@DateAD", DateAD);
            cmd.Parameters.AddWithValue("@CourseID", CourseID);
            cmd.Parameters.AddWithValue("@SemsterID", SemsterID);

            dal.InsertExam(cmd);  
        }

CS

protected void Page_Load(object sender, EventArgs e)

    {
        if (!this.IsPostBack)
        {
            DateTime dt = DateTime.Parse("08:30 AM");
            MKB.TimePicker.TimeSelector.AmPmSpec am_pm;
            if (dt.ToString("tt") == "AM")
            {
                am_pm = MKB.TimePicker.TimeSelector.AmPmSpec.AM;
            }
            else
            {
                am_pm = MKB.TimePicker.TimeSelector.AmPmSpec.PM;
            }
            TimeSelector1.SetTime(dt.Hour, dt.Minute, am_pm);
        }
        CourseGridView.DataBind();
    }
    protected void Calendar1_SelectionChanged(object sender, EventArgs e)
    {
        TextBox1.Text = Calendar1.SelectedDate.ToString("ddd", new System.Globalization.CultureInfo("ar-SA"));
        TextBox2.Text= Calendar1.SelectedDate.ToString("yyyy/MM/dd", new System.Globalization.CultureInfo("ar-SA"));
        TextBox3.Text = Calendar1.SelectedDate.ToString("yyyy/MM/dd");
    }
    protected void Submit(object sender, EventArgs e)
    {
        DateTime start = DateTime.Parse(string.Format("{0}:{1}", TimeSelector1.Hour, TimeSelector1.Minute));
        DateTime end = DateTime.Parse(string.Format("{0}:{1}", TimeSelector2.Hour, TimeSelector2.Minute));

        TimeSpan du = end - start;
        double r = du.TotalHours;

        EndTime.Text = r.ToString();

        b.EWeekday = TextBox1.Text;
       b.BegainTime = Convert.ToDateTime(start);
      b.EndTime = Convert.ToDateTime(end);
        b.Duration = Convert.ToInt32(r);
        b.DateAD = Convert.ToDateTime(TextBox3.Text);
        b.CourseID = Convert.ToInt32(CourseGridView.SelectedValue);
        b.SemsterID = Convert.ToInt32(SemsterList.SelectedValue);

        b.InsertExam_record();



    }

and this is my Stored Procedure

[dbo].[InsertExam]
    -- Add the parameters for the stored procedure here

    @EWeekday NVARCHAR (50),
    @BegainTime Time,
    @EndTime Time,
    @Duration INT,
    @DateAD Date,
    @CourseID INT,
    @SemsterID INT
AS
BEGIN
INSERT INTO Exam
                         ( EWeekday, BegainTime, EndTime, Duration, DateAD, CourseID, SemsterID)
VALUES                   (@EWeekday,@BegainTime,@EndTime,@Duration,@DateAD,@CourseID,@SemsterID)

END