calendar-iso-month-header is a variable defined in `calendar.el'.
Its value is

(propertize (format "%d %s" year (calendar-month-name month)) 'font-lock-face 'calendar-month-header)

  • This variable may be risky if used as a file-local variable.

Default format for calendar month headings with the ISO date style.
Normally you should not customize this, but `calender-month-header'.

You can customize this variable.

This variable was introduced, or its default value was changed, in version 24.4 of Emacs.