System.Threading.Timer time issue

Question

I have an issue with Threading.Timer in my .NET application. To make it easier to understand I made a sample.

using System; using System.Diagnostics; using System.Threading; namespace TimerTestApp { class Program { private static Timer timer; private static int timerTickCounter; private static DateTime timerStartTimer; private static readonly Stopwatch Sw = new Stopwatch(); private static readonly ManualResetEvent TimerFinish = new ManualResetEvent(false); static void Main() { Console.WriteLine("START"); timer = new Timer(TimerCallBack, null, 0, 1000); TimerFinish.WaitOne(); } private static void TimerCallBack(object state) { if (timerTickCounter == 0) { timerStartTimer = DateTime.Now; Sw.Start(); } timerTickCounter++; Console.WriteLine("timerTickCounter = {0}", timerTickCounter); if (timerTickCounter >= 1200) //20.00 min { var secondsSinceStart = (int)(DateTime.Now - timerStartTimer).TotalSeconds; timer.Dispose(); Sw.Stop(); Console.WriteLine("timerTickCounter = {0}; secondsSinceStart={1}; Stowatchseconds={2}", timerTickCounter, secondsSinceStart, Sw.Elapsed.TotalSeconds); Console.ReadLine(); TimerFinish.Set(); } } } }

After running this code I have the very last line with resut:

timerTickCounter = 1200; secondsSinceStart=1215; Stowatchseconds=1215,7573291

As far as you can see timer ticks each second, but the resulting output says it took 15 seconds more time for program to run.

I need mechanism to update DateTime fields, and I cannot simply create a timer which ticks once a second.

Can anyone propose a solution for this?

Approach it from the other side. How much accuracy do you actually need? Do you have a calibration point? — Henk Holterman
– Henk Holterman, Commented Jan 5, 2013 at 17:36
I need an exact accuracy if it is correct to say so. No, I don't have a calibration point. — happy future
– happy future, Commented Jan 5, 2013 at 18:08

Henk Holterman · Accepted Answer · 2013-01-05 17:37:32Z

1

All Timers operate with a ~20ms resolution. So 15 seconds on 20 minutes is inside the expected range.

If you really need a very accurate 1/second timer than you'll need to use a one-shot timer and calculate the remainder of the second each time.

answered Jan 5, 2013 at 17:37

Henk Holterman

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3 Comments

happy future Over a year ago

Would you be so kind to explain it, i don't get it. You mean I need to remember DateTime.Now on each tick and calculate (Now - PrevTime)?

Henk Holterman Over a year ago

Yes. You need to resync, once per hour/minute/second. DateTime.Now is your only fixed reference point.

happy future Over a year ago

Now i got it. Thanks. Never thought that such simple operation will take so much efforts.

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