In Ubuntu 18.04, I see in gnome-tweak-tool I have the option (under Top Bar) to show week numbers in the calendar that appears when I click on the time in the top bar.
My employer (a university) uses numbered weeks but they don't start in January. It varies, but week 1 is usually the week that contains the 1st August (e.g. in 2018/19 week 1 started on 30th July 2018).
It would be useful to have the week numbers displayed in the calendar, but only if I could change the start date so the numbers shown align to those used by my employer. Is it possible to configure the year start date for week numbers?