Timer.cs

namespace MovingForm
{
    public partial class Form1 : Form
    {
        System.Windows.Forms.Timer timer = new();
        DateTime startTime;

        public Form1()
        {
            InitializeComponent();

            timer.Interval = 500;
            timer.Tick += new EventHandler(TimerTick);
            startTime = DateTime.Now;
            timer.Start();
        }

        void TimerTick(object? sender, EventArgs e)
        {
            var distance = DateTime.Now - startTime;
            int milliseconds = distance.Minutes * 60 * 1000 + distance.Seconds * 1000 + distance.Milliseconds;
            Text = milliseconds.ToString();
        }
    }
}