Re: YADTR (Yet Another DateTime Rant)

References	(4 earlier) <mailman.8613.1395917059.18130.python-list@python.org> <lh11s1$kj3$1@news.albasani.net> <CAPTjJmqbD_QYU4P5eQLmdnHcHFzr2w0HfF6JuEuRgMbU2oWx=g@mail.gmail.com> <CANc-5Uys3UgP8s84JiNRkw4t+ecrrLVVtdbwwyuwmt7W9Qg_GQ@mail.gmail.com> <CAPTjJmq95oFsPKO_nD8Dx_oniHaAkMV=QnHK7TiJxr8=s04yfA@mail.gmail.com>
Date	2014-03-27 08:01 -0500
Subject	Re: YADTR (Yet Another DateTime Rant)
From	Skip Montanaro <skip@pobox.com>
Newsgroups	comp.lang.python
Message-ID	<mailman.8618.1395925308.18130.python-list@python.org> (permalink)

Show all headers | View raw

>> There are,
>> as I see it, two common cases where t is negative:
>>
>>   -1 day < t < 0
>>
>> and
>>
>>   t <= -1 day
>
> There are two types of negative numbers: Those closer to zero than -1,
> and those not closer to zero than -1. Yeah, I think those are the most
> common cases. :)

Sorry I wasn't clear. I see two cases w.r.t. *display*, those where
you need to display the number of days back (possibly accounting for
even larger time intervals to make it more human readable), those
where you don't.  Yes, as you observed, they completely cover the
negative timedelta space with two non-overlapping intervals.

Roy's original rant was about how a negative timedelta was
stringified, when what he seemed to care about was mostly the time
interval between now and the previous sunset (which will be less than
a day, unless your day length is advancing -- between the winter and
summer solstices -- and you compute that interval a few seconds before
sunset). The common "how long ago was sunset?" (|delta| < 1 day) case
is handled just fine by my little negate-the-timedelta hack, e.g.:

>>> "-%s" % (-datetime.timedelta(hours=-17, minutes=-12, seconds=-25.234))
'-17:12:25.234000'

Negative timedeltas with a magnitude of one day or more require
something else, perhaps like the ISO8601 duration stuff (which I
personally find distasteful, but that might be the best you can do in
the absence of an anchor datetime).

Skip

Thread

YADTR (Yet Another DateTime Rant) Roy Smith <roy@panix.com> - 2014-03-25 20:58 -0400
  Re: YADTR (Yet Another DateTime Rant) Ethan Furman <ethan@stoneleaf.us> - 2014-03-25 18:19 -0700
  Re: YADTR (Yet Another DateTime Rant) Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-03-26 09:27 +0000
  Re: YADTR (Yet Another DateTime Rant) Skip Montanaro <skip@pobox.com> - 2014-03-26 08:37 -0500
    Re: YADTR (Yet Another DateTime Rant) Roy Smith <roy@panix.com> - 2014-03-26 08:04 -0700
      Re: YADTR (Yet Another DateTime Rant) Skip Montanaro <skip@pobox.com> - 2014-03-26 10:39 -0500
        Re: YADTR (Yet Another DateTime Rant) Marko Rauhamaa <marko@pacujo.net> - 2014-03-26 17:58 +0200
          Re: YADTR (Yet Another DateTime Rant) Skip Montanaro <skip@pobox.com> - 2014-03-26 11:34 -0500
            Re: YADTR (Yet Another DateTime Rant) Marko Rauhamaa <marko@pacujo.net> - 2014-03-26 19:13 +0200
            Re: YADTR (Yet Another DateTime Rant) Grant Edwards <invalid@invalid.invalid> - 2014-03-26 19:12 +0000
              Re: YADTR (Yet Another DateTime Rant) Ben Finney <ben+python@benfinney.id.au> - 2014-03-27 07:06 +1100
      Re: YADTR (Yet Another DateTime Rant) Roy Smith <roy@panix.com> - 2014-03-26 11:50 -0400
  Re: YADTR (Yet Another DateTime Rant) Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2014-03-26 15:02 +0100
    Re: YADTR (Yet Another DateTime Rant) Marko Rauhamaa <marko@pacujo.net> - 2014-03-26 16:43 +0200
  Re: YADTR (Yet Another DateTime Rant) Chris Angelico <rosuav@gmail.com> - 2014-03-27 01:12 +1100
    Re: YADTR (Yet Another DateTime Rant) Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2014-03-27 11:08 +1300
  Re: YADTR (Yet Another DateTime Rant) Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2014-03-26 19:25 -0400
    Re: YADTR (Yet Another DateTime Rant) Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-03-27 00:16 +0000
      Re: YADTR (Yet Another DateTime Rant) Chris Angelico <rosuav@gmail.com> - 2014-03-27 12:28 +1100
        Re: YADTR (Yet Another DateTime Rant) Roy Smith <roy@panix.com> - 2014-03-26 21:38 -0400
          Re: YADTR (Yet Another DateTime Rant) Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-03-27 08:40 +0000
      Re: YADTR (Yet Another DateTime Rant) Dan Sommers <dan@tombstonezero.net> - 2014-03-27 03:56 +0000
      Re: YADTR (Yet Another DateTime Rant) Johannes Bauer <dfnsonfsduifb@gmx.de> - 2014-03-27 11:22 +0100
        Re: YADTR (Yet Another DateTime Rant) Chris Angelico <rosuav@gmail.com> - 2014-03-27 21:44 +1100
          Re: YADTR (Yet Another DateTime Rant) Johannes Bauer <dfnsonfsduifb@gmx.de> - 2014-03-27 12:05 +0100
            Re: YADTR (Yet Another DateTime Rant) Chris Angelico <rosuav@gmail.com> - 2014-03-27 22:33 +1100
          Re: YADTR (Yet Another DateTime Rant) Johannes Bauer <dfnsonfsduifb@gmx.de> - 2014-03-27 12:25 +0100
            Re: YADTR (Yet Another DateTime Rant) Chris Angelico <rosuav@gmail.com> - 2014-03-27 22:42 +1100
            Re: YADTR (Yet Another DateTime Rant) Skip Montanaro <skip@pobox.com> - 2014-03-27 06:56 -0500
              Re: YADTR (Yet Another DateTime Rant) Marko Rauhamaa <marko@pacujo.net> - 2014-03-27 16:04 +0200
            Re: YADTR (Yet Another DateTime Rant) Chris Angelico <rosuav@gmail.com> - 2014-03-27 23:20 +1100
            Re: YADTR (Yet Another DateTime Rant) Skip Montanaro <skip@pobox.com> - 2014-03-27 08:01 -0500
            Re: YADTR (Yet Another DateTime Rant) Terry Reedy <tjreedy@udel.edu> - 2014-03-27 17:10 -0400
            Re: YADTR (Yet Another DateTime Rant) Ethan Furman <ethan@stoneleaf.us> - 2014-03-27 17:04 -0700
            Re: YADTR (Yet Another DateTime Rant) Terry Reedy <tjreedy@udel.edu> - 2014-03-27 21:46 -0400
              Re: YADTR (Yet Another DateTime Rant) Roy Smith <roy@panix.com> - 2014-03-27 21:59 -0400
                Re: YADTR (Yet Another DateTime Rant) Terry Reedy <tjreedy@udel.edu> - 2014-03-27 22:24 -0400
                Re: YADTR (Yet Another DateTime Rant) Chris Angelico <rosuav@gmail.com> - 2014-03-28 14:03 +1100
          Re: YADTR (Yet Another DateTime Rant) Roy Smith <roy@panix.com> - 2014-03-27 08:52 -0400
            Re: YADTR (Yet Another DateTime Rant) Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2014-03-27 15:12 +0100
            Re: YADTR (Yet Another DateTime Rant) Chris Angelico <rosuav@gmail.com> - 2014-03-28 01:15 +1100
            Re: YADTR (Yet Another DateTime Rant) Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-03-27 23:41 +0000
              Re: YADTR (Yet Another DateTime Rant) Roy Smith <roy@panix.com> - 2014-03-27 20:29 -0400
                Re: YADTR (Yet Another DateTime Rant) Ben Finney <ben+python@benfinney.id.au> - 2014-03-28 11:43 +1100
                Re: YADTR (Yet Another DateTime Rant) Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-03-28 11:11 +0000
                Re: YADTR (Yet Another DateTime Rant) Roy Smith <roy@panix.com> - 2014-03-28 08:30 -0400
                Re: YADTR (Yet Another DateTime Rant) Marko Rauhamaa <marko@pacujo.net> - 2014-03-28 15:10 +0200
                Re: YADTR (Yet Another DateTime Rant) Chris Angelico <rosuav@gmail.com> - 2014-03-29 00:19 +1100
                Re: YADTR (Yet Another DateTime Rant) Roy Smith <roy@panix.com> - 2014-03-28 09:22 -0400
                Re: YADTR (Yet Another DateTime Rant) Rustom Mody <rustompmody@gmail.com> - 2014-03-28 06:30 -0700
                Re: YADTR (Yet Another DateTime Rant) Chris Angelico <rosuav@gmail.com> - 2014-03-29 00:32 +1100
                Re: YADTR (Yet Another DateTime Rant) Roy Smith <roy@panix.com> - 2014-03-28 09:20 -0400
                Re: YADTR (Yet Another DateTime Rant) Marko Rauhamaa <marko@pacujo.net> - 2014-03-28 16:34 +0200
                Re: YADTR (Yet Another DateTime Rant) Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-03-28 14:35 +0000
                Re: YADTR (Yet Another DateTime Rant) Chris Angelico <rosuav@gmail.com> - 2014-03-29 02:25 +1100
  Re: YADTR (Yet Another DateTime Rant) Ethan Furman <ethan@stoneleaf.us> - 2014-03-26 16:33 -0700

csiph-web