displayedCalendarSystem

Which calendar the grid shows.

Only the display changes: selectedDate stays a Bikram Sambat date whichever calendar is on screen, so switching keeps the same day selected and leaves nepaliSelectableDates rules working unchanged. The grid re-anchors on the selected date, or on the visible month when there is no selection.

Defaults to CalendarSystem.BIKRAM_SAMBAT. The default implementation here is inert, so a custom implementation of this interface keeps compiling but will not respond to the picker's calendar switch until it overrides this.