Option to set the first day of the week in the Planning calendar

Currently, the Planning calendar always starts the week on Sunday. However, in many countries (including Ukraine and most of Europe), the standard first day of the week is Monday, following the ISO 8601 standard.
It would be very helpful to have an option in the settings to choose the first day of the week — either Sunday or Monday — so the calendar matches the regional standard that each church is used to.

Please add a setting to change the first day of the week in the Planning calendar (Sunday / Monday).