Calendar: where is the "week starts on Monday" setting?

Could somebody please help me find the « week starts on Monday » setting? Thank you

P.S. Also, if possible, please let me know how we can change date format on Axelor to ISO format, i.e. YYYY-MM-DD.

Date format in Axelor depends on browser locale. So you can change according to that.

but where the calendar settings? How to set up it to start week on monday (not on sunday)