Re: [BUGS] BUG #14632: Plus and minus operators inconsistency withleap years and year intervals.

On Thu, Apr 27, 2017 at 1:01 AM, Pietro Pugni <pietro.pugni@gmail.com> wrote:

Expect 1912-02-28 is a correct response.  The only reason you think the 29th comes into play here is because you remember that the starting point was the 29th.  The system has no such memory.

And this is logically wrong because it leads to wrong results. I’m aware that time intervals are difficult to manage but more exactness is needed here: '10 years' must have the same meaning when added to a date and subtracted from it, otherwise it leads to wrong results. 

Your suggestion just moves the wrong results to another use case; see my response upthread.  There is no objectively correct answer here, like you seem to think.

I just found this query clearly shows the underlying algorithm is somewhat wrong:

(I)

postgres=# select age('2017-01-30'::date, '1912-02-29'::date) + '1912-02-29'::date;

      ?column?       

---------------------

 2017-01-30 00:00:00

(II)

postgres=# select age('2017-02-01'::date, '1912-02-29'::date) + '1912-02-29'::date;

      ?column?       

---------------------

 2017-01-30 00:00:00

Query (II) should return 2017-02-01 instead of 2017-01-30 and the two queries should return different results.

More generally, ...

I understand why this happens (this has been discussed previously) but clearly there’s something wrong..