bug#12318: gnu date has incorrect date when using date math during a leap year

[Bob Proulx]

SciFi wrote:
> I am just a passerby here.  But when I see these specific
> kinds of "errors", especially due to "month" usages, I always
> have a thought:  How would we make GNU-date to operate on the
> Month Number Itself when we type "month" in the --date string,
> and stop its assumption that we mean "30 days" by this usage? 
> We would not need to do this fooling-around with the Day-15
> trick as shown.

I understand the sentiment.  My personal one is that the "human"
language relative date code wasn't very well thought out and should
not have been released in the present form.  I also believe that
behavior change in long standing code is to be avoided since it breaks
so many things.  However this one is trouble to use correctly though
so I think changing it couldn't hurt too much.

> I think this is where the "misusage" is being done by us
> plain-ol' folk.  ;)

I think you are suggesting 2012-08-31 -1 month would end up with
2012-07-31, right?  Makes sense to me.  Hard to argue with it.  Right
up until 2012-08-31 -2 months comes along.  Is that 2012-06-31?  Or
2012-06-30 by force of will?  Or 2012-07-01 by math?  Or throw it as
an invalid date?  (Which I think would be less friendly.)  Or?  :-) 
It isn't a simple problem.

It would be great if there were some really smart artificially
intelligent program to process it.  It would have to smarter than a
human because even humans can't agree on this.

> I hope I've expressed correctly what I mean with this thought.
> (And I know: "Patches welcome." <g>)
> Thanks for letting me interject my thought on this.

I think it was a very good comment.

Bob