You have to subscribe to the valuechanged event to do what you like
private void Form1_Load(object sender, EventArgs e)
{
var timePicker = new DateTimePicker();
timePicker.Format = DateTimePickerFormat.Time;
timePicker.ShowUpDown = true;
timePicker.Location = new Point(10, 10);
timePicker.Width = 100;
timePicker.ValueChanged += timePicker_ValueChanged;
Controls.Add(timePicker);
}
void timePicker_ValueChanged(object sender, EventArgs e)
{
var picker = (DateTimePicker) sender;
if (picker == null) return;
DateTime d = DateTime.Now;
var ts = d.Subtract(picker.Value);
System.Diagnostics.Debug.WriteLine("We get a total of {0} seconds", (int) ts.TotalSeconds);
}