How to change regional settings in Linux, including decimal point

I was on Linux Mint, now I'm trying Ubuntu 18 main distro. At top of Gnome day of week/time is displayed. That's where I started, wanting to change it to English having set regional to Russian via GUI, as by the way I noticed time zone changes if I changed regional to US. I've read and tried this: How to get current or set wanted regional format in the terminal? Strangely, after sudo update-locale LC_TIME=en_CA.UTF-8 and even restart of PC, /etc/default/locale has CA, but locale in bash gives RU. And day of week on top of screen is in Russian still. Why different in file and by command? How to change language on top of screen, is it some short date variable, where to find it? As extension to above, is it possible and how to change decimal point and thousand separator each individually to what I like?