SqlDateTime overflow Error on simple LINQ, C# .Net Web Page

I have a simple page I'm creating that just inserts some data from textboxes in .Net using C#. I get the overflow error stating the date must be within a specific range. The text being entered in the txtBirthdate box would be something like: 01/01/1980.

When debugging, the Client1 _Birthdate object shows {1/1/1980 12:00:00}. So as far as I can tell it's doing what it's supposed to. Thanks in advance for any help.

protected void Button1_Click(object sender, EventArgs e)
{
    DataClasses1DataContext db = new DataClasses1DataContext();

    Client client1 = new Client
    {
        FirstName = txtFirstName.Text.ToString(),
        LastName = txtLastName.Text.ToString(),
        MiddleInitial = Convert.ToChar(txtMI.Text),
        Alias = txtAlias.Text.ToString(),
        Address = txtAddress.Text.ToString(),
        City = txtCity.Text.ToString(),
        State = txtState.Text.ToString(),
        Zip = Convert.ToInt32(txtZip.Text),
        Phone = txtPhone.Text.ToString(),
        Birthdate = Convert.ToDateTime(txtBirthdate.Text.ToString()),
        SSN = Convert.ToInt32(txtSSN.Text),
        DLNumber = txtDLNumber.Text.ToString(),
        Gender = Convert.ToByte(ddGender.Text),
        PrimaryRace = Convert.ToByte(ddPrimaryRace.Text),
        SecondaryRace = Convert.ToByte(ddSecondaryRace.Text),
        Ethnicity = Convert.ToByte(ddEthnicity.Text),
        Veteran = Convert.ToBoolean(ddVeteranStatus.Text),
        HoH = Convert.ToBoolean(ddHoH.Text)
    };

    db.Clients.InsertOnSubmit(client1);
    db.SubmitChanges();
}