calendar-intermonth-header is a variable defined in `calendar.el'.
Its value is
nil
This variable may be risky if used as a file-local variable.
Documentation:
Header text to display in the space to the left of each calendar month.
See `calendar-intermonth-text'.
You can customize this variable.
This variable was introduced, or its default value was changed, in
version 23.1 of Emacs.