Re: [PATCH] ISO 8601 basic format and decimal hours, minutes

[Assaf Gordon <assafgordon@gmail.com>]

Hello Alex,

Thank for you putting the time for writing the patch
and descriptions in such details.

In general:

On 2019-02-18 9:00 p.m., Alex Eulenberg wrote:
> 1. Accept dates in the ISO 8601 basic date and time format.
[...]> 2. Accept decimal fractions of time units other than seconds in
> accordance with ISO 8601.
[...]
> Forms no longer accepted as a result of the patch:
[...]
> input                  current output              output with patch
> "20180102 00-03"       2018-01-02T03:00+00 +       (rejected)
> "20180102 04-03"       2018-01-02T07:00+00 +       (rejected)
[...]
> 
> input                  current output              output with patch
> "20180102T00-03"       (rejected)                  2018-01-02T03:00+00
> "20180102T04-03"       (rejected)                  2018-01-02T07:00+00

Adding new accepted formats is good,
but rejecting (or changing the meaning of) currently-accepted formats
is a much more problematic decision due to breaking existing programs.

I think that before continuing, it should be discussed and decided
whether this is acceptable or not (Paul, Jim?).

If we do go forward this this breaking-change, we should make sure
to announce it and communicate it properly to users of coreutils' date(1).

As a compromise, note that the 'parse_datetime2' function accepts
'flags' parameter (added in recent years). Perhaps a flag could
be specified if 'T' is always iso8601 or military time
(and then add an option to date(1) ).


> 2. For inputs of form "(YY)YYMMDD'T'hhmm" the current version of
> parse-datetime interprets the "T" as the single-letter military time zone
> identifier equivalent to zone offset +0700. This is probably never the
> intention.

Not so, 'T' has special handling code, and in some of the cases
is explicitly translated to HOUR(7):
https://git.savannah.gnu.org/cgit/gnulib.git/tree/lib/parse-datetime.y#n751


>   doc/parse-datetime.texi     |  17 ++--
>   lib/parse-datetime.y        | 193 ++++++++++++++++++++++++++++++------
>   tests/test-parse-datetime.c | 115 +++++++++++++++++++++
>   3 files changed, 291 insertions(+), 34 deletions(-)

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regards,
  - assaf