Unify the DatePickerDisplays

There are multiple datepickers around the site. Some of them seems to display working week from Sunday, some from Monday. Additionally, Firefox displays red days (Sat/Sun) Chrome does not. It would be good to find out a coherent way to deal with it:

MyShifts:

• TimeReport Tab
• ShiftExport

RotaMaker:

• Desidarata YearlyOverview
• Desiderata Export
• Time Report
• Team Statistics
• Shift Inconsistencies (patterns)
• Shift Swaps
• Planning Edits
  • Export
  • Shifts status update: FROM and UNTIL
  • Merge revisions NEW start date
  • Remove schedules FROM and UNTIL