DateTimeFormatter is super slow

Question

Why is UWP's DateTimeFormatter so slow at formatting times to strings?

   DateTimeFormatter.ShortTime.Format(time)  

If you try formatting 1,440 different times in a loop, that loop takes 2.5 seconds to complete.

If you just use DateTime.ToString("t"), that same loop takes 0 seconds.

Since we seemingly have to use this DateTimeFormatter class to get properly localized times, it'd be nice if it performed reasonably.

Answer 1

Hello,​

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You could create a set of tasks that format times in an array. The tasks are stored in a List collection that is passed to the WhenAll(IEnumerable) method. When you call the Wait method, all the thread run synchronously, it will speed up operations. For example:

Debug.WriteLine(DateTime.Now.ToString("hh:mm:ss.ff"));  
var tasks = new List();​  
for (int i = 0; i < 1440; i++) {​  
    tasks.Add(Task.Run(() =>​  
    {​  
        DateTimeOffset dateAndTime = new DateTimeOffset(1970+i, 5, 1, 8, 6, 32,​  
                                                 new TimeSpan(1, 0, 0));​  
        DateTimeFormatter.ShortTime.Format(dateAndTime);​  
    }));​  
}​  
Task t = Task.WhenAll(tasks);​  
t.Wait();​  
Debug.WriteLine(DateTime.Now.ToString("hh:mm:ss.ff"));  

Output:

10:06:02.40

10:06:02.66