[issue39484] time_ns() and time() cannot be compared on windows

[Vincent Michel]

Vincent Michel <vxgmichel at gmail.com> added the comment:

I thought about it a bit more and I realized there is no way to recover the time in hundreds of nanoseconds from the float produced by `time.time()` (since the windows time currently takes 54 bits and will take 55 bits in 2028). 

That means `time()` and `time_ns()` cannot be compared by converting time() to nanoseconds, but it might still make sense to compare them by converting time_ns() to seconds (which is apparently broken at the moment).

If that makes sense, a possible roadmap to tackle this problem would be:
- fix `_PyTime_AsSecondsDouble` so that `time.time_ns() / 10**9 == time.time()`
- add a warning in the documentation that one should be careful when comparing the timestamps produced by `time()` and time_ns()` (in particular, `time()` should not be converted to nanoseconds)

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue39484>
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