Inserting Dates From Asp.net Application To SQL Server Db, Help.

 Hi Guys,
I need some help here. I've created a asp.net reception system for internal use. The problem I'm having is this, when I update a record all the dates are saved as 01/01/1900. I've had a look at a couple of threads on various forums and sites but none of them seem to have a solution for my problem...
I have an AJAX calenderExtenders on the date text boxes and i have played around with all different date formats, currently on yyyy/MM/dd. I've also tried DateTime.Parse(txtStartDate.text) but doesn't work. I pass all the parameters to a stored procedure on the sql server in the correct order. I've included my code below, I have only included date parameters.
 SqlConnection conn = null;

        try
        {
            string connString =
                ConfigurationManager.ConnectionStrings["RCM"].ConnectionString;

            //Initialise the sqlConnection object
            conn = new SqlConnection();
            conn.ConnectionString = connString; //Getting connection string to the db

            //Create the command
            SqlCommand command = new SqlCommand("UpdateClient", conn);
            command.CommandType = CommandType.StoredProcedure;

            //Opening connection to the db
            conn.Open();

            //Setting input parameters                    
         
            command.Parameters.AddWithValue("@DOB", txtDOB.Text);
            command.Parameters.AddWithValue("@StartDate",txtStartDate.Text);
           
            //Execute T-SQL
            command.ExecuteNonQuery();

            //Close connection
            command.Connection.Close();
            conn.Close();
        }

        catch (Exception ex)
        {
            lblError.Text = "An error has occured: " + ex.Message;
        }