I can confirm this bug.
SOGo WebGUI shows week number 12 now, but it is 11.

SOGo should use Unix system command 'date "+%V" which returns correct number of the week in ISO 8601.
You could find interesting table on
http://www.pjh2.de/datetime/weeknumber/wnc.php?l=en#Legend
I consider ISO 8601 for the best variant.

Aha - now I found I had not set any SOGoFirstWeekOfYear variable, so defalut value "January1" is using. That is wrong for Czech Rep.
When I set it to "First4DayWeek", Calendar week is fine for all users who didn't save their preferences in WebGUI in the past. For them I can do:

• sogo-tool backup
• change SOGoFirstWeekOfYear = First4DayWeek;
• sogo-tool -p restore

and it will be ok for all.

Milos

Instead of backup and restore you can iterate through each user with a wrong setting:

[sogo@machine ~]$ /usr/sbin/sogo-tool user-preferences set defaults ${userID} SOGoFirstWeekOfYear First4DayWeek

With this you don't rely on the user to not edit his account data while changing this preference.

I tried it, but I got following error [on SOGo-1.3.16]

/usr/local/sbin/sogo-tool user-preferences set defaults kur SOGoFirstWeekOfYear First4DayWeek
Jun 18 15:34:30 sogo-tool [6421]: <0x0xae7200[SOGoCache]> Cache cleanup interval set every 300.000000 seconds
Jun 18 15:34:30 sogo-tool [6421]: <0x0xae7200[SOGoCache]> Using host(s) 'localhost' as server(s)
Jun 18 15:34:30 sogo-tool [6421]: [ERROR] <0x0x942790[GSCBufferString]> json parser: Unrecognised leading character, attempting once more after unescaping...
Jun 18 15:34:30 sogo-tool [6421]: [ERROR] <0x0x942790[GSCBufferString]> total failure. Original string is: First4DayWeek
2012-06-18 15:34:30.294 sogo-tool[6421] Invalid JSON input - no changes performed in the database. The supplied value was: First4DayWeek

You must provide JSON input to sogo-tool.

First, do a "get" and understand what you're trying to set, then do it.

I tried to find something about it documentation - I didn't find.
'sogo-tool --help' doesn't provide any information about JSON or get.
(and I don't want to analyze source code for this now).

sogo-tool user-preferences get ...

Sorry, should have been precise:

/usr/sbin/sogo-tool user-preferences set defaults ${userID} SOGoFirstWeekOfYear '{"SOGoFirstWeekOfYear": "First4DayWeek"}'