double nTotalSeconds = 90; DateTime dt; private void Form_Load(object sender, EventArgs e) { dt = new DateTime(); timer1.Interval = 1000; timer1.Enabled = true; } private void timer1_Tick(object sender, EventArgs e) { nTotalSeconds--; textBox1.Text = dt.AddSeconds(nTotalSeconds).ToString("HH:mm:ss"); if(nTotalSeconds == 0) timer1.Enabled = false; } 출력 00:01:30 00:01:29 00:..