>>OK., should have said that it won't always work
>>
>>Try to add 6 months to 31/08/2015 - that would become 31/02/2016
>
>Well, it still works.
>
>See attached. The date is 31/08/2015. The next cell adds six months to it.


Don't think so

Aug 2015 + 6 months is Feb 2016 not March imo

attached
(1) Your formula - gives 02/03/2016

(2) With edate() - gives 29/02/2016