[Python-ideas] High Precision datetime

Chris Barker chris.barker at noaa.gov
Thu May 17 12:49:09 EDT 2018

On Tue, May 15, 2018 at 11:21 AM, Rob Speer <rspeer at luminoso.com> wrote:

> I'm sure that the issue of "what do you call the leap second itself" is
> not the problem that Chris Barker is referring to. The problem with leap
> seconds is that they create unpredictable differences between UTC and real
> elapsed time.
> You can represent a timedelta of exactly 10^8 seconds, but if you add it
> to the current time, what should you get? What UTC time will it be in 10^8
> real-time seconds? You don't know, and neither does anybody else, because
> you don't know how many leap seconds will occur in that time.

indeed -- even if you only care about the past, where you *could* know the
leap seconds -- they are, by their very nature, of second precision --
which means right before leap second occurs, your "time" could be off by up
to a second (or a half second?)

It's kind of like using a carpenter's tape measure to to locate points from
a electron microscope scan :-)

The other issue with leap-seconds is that python's datetime doesn't support
them :-)

And neither do most date-time libraries.



Christopher Barker, Ph.D.

Emergency Response Division
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Chris.Barker at noaa.gov
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