.NET, event every minute (on the minute). Is a timer the best option?

Question

Building on the answer from aquinas which can drift and which doesn't tick exactly on the minute just within one second of the minute:

static System.Timers.Timer t;

static void Main(string[] args)
{
    t = new System.Timers.Timer();
    t.AutoReset = false;
    t.Elapsed += new System.Timers.ElapsedEventHandler(t_Elapsed);
    t.Interval = GetInterval();
    t.Start();
    Console.ReadLine();
}

static double GetInterval()
{
    DateTime now = DateTime.Now;
    return ((60 - now.Second) * 1000 - now.Millisecond);
}

static void t_Elapsed(object sender, System.Timers.ElapsedEventArgs e)
{
    Console.WriteLine(DateTime.Now.ToString("o"));
    t.Interval = GetInterval();
    t.Start();
}

On my box this code ticks consistently within .02s of each minute:

2010-01-15T16:42:00.0040001-05:00
2010-01-15T16:43:00.0014318-05:00
2010-01-15T16:44:00.0128643-05:00
2010-01-15T16:45:00.0132961-05:00

How about:

int startin = 60 - DateTime.Now.Second;
var t = new System.Threading.Timer(o => Console.WriteLine("Hello"), 
     null, startin * 1000, 60000);

Creating a Timer control that fires every 1 second (and usually does nothing but a simple check) will add negligible overhead to your application.

Simply compare the value of Environment.TickCount or DateTime.Now to the last stored time (the previous 'minute tick'), and you should have a reasonably precise solution. The resolution of these two time values is about 15ms, which should be sufficient for your purposes.

Do note however that the interval of the Timer control is not guaranteed to be that precise or even anywhere now, since it runs on the Windows message loop, which is tied in with the responsiveness of the UI. Never rely on it for even moderately precise timing - though it is good enough for firing repeating events where you can check the time using a more sensitive method such as one of the two given above.

You can nail this with reactive extensions which will take care of lots of timer related problems for you (clock changes, app hibernation etc). Use Nuget package Rx-Main and code like this:

Action work = () => Console.WriteLine(DateTime.Now.ToLongTimeString());

Scheduler.Default.Schedule(
    // start in so many seconds
    TimeSpan.FromSeconds(60 - DateTime.Now.Second), 
    // then run every minute
    () => Scheduler.Default.SchedulePeriodic(TimeSpan.FromMinutes(1), work));               

Console.WriteLine("Press return.");
Console.ReadLine();

Read here (search for "Introducing ISchedulerPeriodic") to see all the issues this is taking care of: http://blogs.msdn.com/b/rxteam/archive/2012/06/20/reactive-extensions-v2-0-release-candidate-available-now.aspx

I jsut wrote this class using the WPF DispatcherTimer but you can swap the dispatcher for any timer that supports changing when it's woken from sleep state.

The class is constructed with a fixed time step and supprts Start/Stop/Reset, Start/Stop/Start works like a resume operation. The timer is like a stopwatch in that regard.

A clock implementation would simply create the class with a interval of 1 second and listen to the event. Be wary though that this is a real-time clock, if the tick event takes longer than the interval to finish you'll notice that the clock will try and catch up to real-time this will cause a burst of tick events being raised.

public class FixedStepDispatcherTimer
{
    /// <summary>
    /// Occurs when the timer interval has elapsed.
    /// </summary>
    public event EventHandler Tick;

    DispatcherTimer timer;

    public bool IsRunning { get { return timer.IsEnabled; } }

    long step, nextTick, n;

    public TimeSpan Elapsed { get { return new TimeSpan(n * step); } }

    public FixedStepDispatcherTimer(TimeSpan interval)
    {
        if (interval < TimeSpan.Zero)
        {
            throw new ArgumentOutOfRangeException("interval");
        }
        this.timer = new DispatcherTimer();
        this.timer.Tick += new EventHandler(OnTimerTick);
        this.step = interval.Ticks;
    }

    TimeSpan GetTimerInterval()
    {
        var interval = nextTick - DateTime.Now.Ticks;
        if (interval > 0)
        {
            return new TimeSpan(interval);
        }
        return TimeSpan.Zero; // yield
    }

    void OnTimerTick(object sender, EventArgs e)
    {
        if (DateTime.Now.Ticks >= nextTick)
        {
            n++;
            if (Tick != null)
            {
                Tick(this, EventArgs.Empty);
            }
            nextTick += step;
        }
        var interval = GetTimerInterval();
        Trace.WriteLine(interval);
        timer.Interval = interval;
    }

    public void Reset()
    {
        n = 0;
        nextTick = 0;
    }

    public void Start()
    {
        var now = DateTime.Now.Ticks;
        nextTick = now + (step - (nextTick % step));
        timer.Interval = GetTimerInterval();
        timer.Start();
    }

    public void Stop()
    {
        timer.Stop();
        nextTick = DateTime.Now.Ticks % step;
    }
}