Allow changing the start of the week to Monday
An issue was reported to GNOME Calendar that asked for the ability to change the start of the week from Sunday to Monday on en_US.UTF-8 locales, and @feaneron closed it since it is considered a system locale issue rather than an application-specific one.
Therefore, it should be possible to change this from the system settings menu. The setting should default to the locale default, but the user should be able to change it similar to how you can change the AM/PM vs 24-hour-time format.
Proposed mockup
Sorry for the bad quality, I'm bad at Inkscape but hopefully this gets the idea across.