C# .NET 2 Threading.Timer - time drifting
public void MyTimerCallback(object something) {
    var now = DateTime.UtcNow;
    var shouldProbablyHaveRun = new DateTime(
        now.Year, now.Month, now.Day,
        now.Hour, now.Minute - (now.Minute % 10), 0);
    var nextRun = shouldProbablyHaveRun.AddMinutes(10.0);

    // Do stuff here!

    var diff = nextRun - DateTime.UtcNow;
    timer.Change(diff, new TimeSpan(-1));
}

if (DateTime.Now.Minute % 10) == 0

while ((DateTime.Now - lastRunTime).TotalSeconds < 600)
     CurrentThread.Sleep(1000);

public static void Main()
{
    System.Timers.Timer aTimer = new System.Timers.Timer();
    aTimer.Elapsed+=new ElapsedEventHandler(OnTimedEvent);
    // Set the Interval to 600 seconds.
    aTimer.Interval=600000;
    aTimer.Enabled=true;

    Console.WriteLine("Press 'q' to quit the sample.");
    while(Console.Read()!='q');
}

// Specify what you want to happen when the Elapsed event is raised.
private static void OnTimedEvent(object source, ElapsedEventArgs e)
{
    Console.WriteLine("10 minutes passed!");
}