Alexander Belopolsky wrote:
> 
> Alexander Belopolsky <alexander.belopolsky@gmail.com> added the comment:
> 
> On Mon, Apr 9, 2012 at 6:20 PM, Marc-Andre Lemburg
> <report@bugs.python.org> wrote:
>> Which is wrong, since the start of the first ISO week of a year
>> can in fact start in the preceeding year...
> 
> Hmm, the dateutil documentation seems to imply that relativedelta
> takes care of this:
> 
> http://labix.org/python-dateutil#head-72c4689ec5608067d118b9143cef6bdffb6dad4e
> 
> (Search the page for "ISO")

That's not realtivedelta taking care of it, it's the way it is
used: the week with 4.1. in it is the first ISO week of a year;
it then goes back to the previous Monday and adds 14 weeks from
there to go to the Monday of the 15th week. This works fine as
long as 4.1. doesn't fall on a Monday...

You don't really expect anyone to remember such rules, do you ? :-)