Cookie Expiration Date

My cookie's expiration date is not setting correctly, although it is expiring correctly. Can you help? Thanks.
       protected void Page_Load(object sender, EventArgs e)         {             StringBuilder sb = new StringBuilder();             // Get cookie from the current request.             HttpCookie cookie = Request.Cookies.Get("The cookie");             if (cookie == null)             {                 sb.Append("The cookie was not found and has been created. Creating cookie to add to the respo ...