cal -w and ISO weeks

Hi,

fiddling around with 'cal -w' made me stumble in 2021:

% cal -w 1 2021

      January 2021     
   Su Mo Tu We Th Fr Sa
 1                 1  2
 2  3  4  5  6  7  8  9

3 10 11 12 13 14 15 16
4 17 18 19 20 21 22 23
5 24 25 26 27 28 29 30
6 31

Obviously these week numbers are not ISO weeks. The manpage says:

-w, --week[=number]
Display week numbers in the calendar (US or ISO-8601).

So the next thing I tried was:

% cal --iso -w 1 2021

      January 2021     
   Su Mo Tu We Th Fr Sa
 1                 1  2
 2  3  4  5  6  7  8  9

3 10 11 12 13 14 15 16
4 17 18 19 20 21 22 23
5 24 25 26 27 28 29 30
6 31

I actually had to read the OpenBSD man pages to see what's going on:

-w Display week numbers in the month display. If -m is specified
the ISO week format is assumed. The options -j and -w are mutually exclusive.

Finally:

% cal -m -w 1 2021

      January 2021     
   Mo Tu We Th Fr Sa Su
53              1  2  3
 1  4  5  6  7  8  9 10

2 11 12 13 14 15 16 17
3 18 19 20 21 22 23 24
4 25 26 27 28 29 30 31

So, to avoid further confusion, I'd propose to:

1) Reword the description of -w in the man page cal(1).

2) Rethink if --iso shouldn't also imply -m, as implied by ISO-8601.

Thanks,

Leah Neukirchen  <[email protected]>  https://leahneukirchen.org/

Fixed (we already have a note about it in NOTES section, but it's somehow pretty hidden at the first glance).
https://github.com/karelzak/util-linux/commit/261cf856277f5e7e4815c211fe48b97746d5d3a3

Good point, sounds like user-friendly change (although it is not 100% backwardly compatible).

William, what about to automatically use -m (start week at Monday) when --iso specified on command line? It means not keep --iso only as way to switch calendars, but also as a general option to get ISO-8601. (Not sure, may be we already discussed this years ago.)

Karel

 Karel Zak  <[email protected]>
 http://karelzak.blogspot.com