[Numpy-discussion] NumPy date/time types and the resolution concept

Anne Archibald peridot.faceted@gmail....
Tue Jul 15 10:54:40 CDT 2008

2008/7/15 Francesc Alted <faltet@pytables.org>:

> Maybe is only that.  But by using the term 'frequency' I tend to think
> that you are expecting to have one entry (observation) in your array
> for each time 'tick' since time start.  OTOH, the term 'resolution'
> doesn't have this implication, and only states the precision of the
> timestamp.

> Well, after reading the mails from Chris and Anne, I think the best is
> that the origin would be kept as an int64 with a resolution of
> microseconds (for compatibility with the ``datetime`` module, as I've
> said before).

A couple of details worth pointing out: we don't need a zillion
resolutions. One that's as good as the world time standards, and one
that spans an adequate length of time should cover it. After all, the
only reason for not using the highest available resolution is if you
want to cover a larger range of times. So there is no real need for
microseconds and milliseconds and seconds and days and weeks and...

There is also no need for the origin to be kept with a resolution as
high as microseconds; seconds would do just fine, since if necessary
it can be interpreted as "exactly 7000 seconds after the epoch" even
if you are using femtoseconds elsewhere.


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