time difference

private void linkLabel1_LinkClicked(object sender, LinkLabelLinkClickedEventArgs e)

        {

            textBox1.Text = DateTime.Now.ToString();

        }

        private void linkLabel2_LinkClicked(object sender, LinkLabelLinkClickedEventArgs e)

        {

           textBox2.Text= DateTime.Now.ToString();

        }

        private void button1_Click(object sender, EventArgs e)

        {

            TimeSpan ts;

            ts = Convert.ToDateTime(textBox2.Text) - Convert.ToDateTime(textBox1.Text);

            textBox3.Text = ts.ToString();

        }