GitLab

* lisp/calendar/calendar.el (calendar-american-month-header)
(calendar-european-month-header, calendar-iso-month-header)
(calendar-month-header): New options.
(calendar-set-date-style): Set calendar-month-header.  Redraw calendar.
(calendar-generate-month): Use calendar-month-header.

Fixes: debbugs:9510