[Python-Dev] Aware datetime from naive local time Was: Status on PEP-431 Timezones (original) (raw)

Alexander Belopolsky alexander.belopolsky at gmail.com
Mon Apr 13 21:14:23 CEST 2015

On Mon, Apr 13, 2015 at 2:05 PM, Chris Barker <chris.barker at noaa.gov> wrote:

However, different UTC times may map to the same wall time and some

expressible wall times are not results of a map of any UTC time.

got it. I suggest you perhaps word it something like: walltime = f( location, utctime) and utctime = f( location, utctime ) These are two different problems, and one is much harder than the other! (though both are ugly!)

You probably meant "utc_time = f( location, wall_time)" in the last equation, but that would still be wrong. A somewhat more correct equation would be

utc_time = f^(-1)( location, wall_time)

where f^(-1) is the inverse function of f, but since f in not monotonic, no such inverse exists.

Finding the inverse of f is the same as solving the equation f(x) = y for any given y. If f is such that this equation has only one solution for all possible values of y then an inverse exists, but this is not so in our case. -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://mail.python.org/pipermail/python-dev/attachments/20150413/7e265695/attachment.html>

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