[Python-ideas] High Precision datetime

[Chris Angelico]

On Tue, May 15, 2018 at 2:05 AM, Chris Barker via Python-ideas
<python-ideas at python.org> wrote:
> But my question is whether high precision timedeltas belongs with "calendar
> time" at all.
>
> What with UTC and leap seconds, and all that, it gets pretty ugly, when down
> to the second or sub-second, what a given datetime really means.

UTC and leap seconds aren't a problem. When there's a leap second, you
have 23:59:60 (or you repeat 23:59:59, if you can't handle second
#60). That's pretty straight-forward, perfectly well-defined.

No, the REAL problems come from relativity.....

> If I were to work with high precision measurements, experiments, etc, I'd
> use a "nanoseconds since" representation, where the "epoch" would likely be
> the beginning of the experiment, of something relevant.

That's an unrelated form of time calculation. For that kind of thing,
you probably want to ignore calendars and use some form of monotonic
time; but also, if you want to go to (or below) nanosecond resolution,
you'll need your clock to actually be that accurate, which most likely
means you're not using a computer's clock. Femtosecond timestamping
would basically be just taking numbers given to you by an external
device and using them as sequence points - clocks and calendars become
irrelevant. The numbers might as well be frame numbers in a
super-high-speed filming of the event.

ChrisA