calendar-intermonth-text is a variable defined in `calendar.el'.
Its value is

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

Text to display in the space to the left of each calendar month.
Can be nil, a fixed string, or a lisp expression that returns a string.
When the expression is evaluated, the variables DAY, MONTH and YEAR
are integers appropriate for the first day in each week.
Will be truncated to the smaller of `calendar-left-margin' and
`calendar-intermonth-spacing'. The last character is forced to be a space.
For example, to display the ISO week numbers:

(setq calendar-week-start-day 1
(format "%2d"
(calendar-absolute-from-gregorian (list month day year)))))
'font-lock-face 'font-lock-function-name-face))

See also `calendar-intermonth-header'.

You can customize this variable.

This variable was introduced, or its default value was changed, in version 23.1 of Emacs.