What is the accuracy of the datenum function?

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Phil 2017-2-10

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回答： Peter Perkins 2017-2-13

What is the accuracy of the datenum function? How many decimal places are retained for the seconds portion of time? When evaluating the elapsed time between dates and times, what decimal place in seconds is it accurate to?

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Answer 1

Andreas 2017-2-10

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Milliseconds

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Answer 2

Stephen23 2017-2-10

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编辑：Stephen23 2017-2-10

在 MATLAB Online 中打开

Although not clearly documented, in my experience datenum and friends offer repeatable operations down to milliseconds.

Note that the theoretical limit of the double type is just less than a millisecond:

 >> (3000*365*24*60*60)/pow2(52)
 ans =   2.1007e-005
 >> eps(3000*365)*(24*60*60)
 ans =   2.0117e-005

https://www.mathworks.com/matlabcentral/answers/45765-what-is-the-precision-of-a-matlab-datenum

http://www.mathworks.com/matlabcentral/newsreader/view_thread/250872

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Answer 3

Peter Perkins 2017-2-13

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Phil, unless you're using pre-R2014b, you are probably better off using datetime instead of datenum. As others have said, the practical limit of datenums is on the order of .1ms. This is one of the many improvements that datetime offers: precision down to nanoseconds.