calendar-today-markercalendar-today-marker is a variable defined in `
calendar.el'. Its value is
calendar-todayDocumentation: How to mark today's date in the calendar. The value can be either a single-character string (e.g. "=") or a face. Used by `calendar-mark-today'. You can customize this variable. This variable was introduced, or its default value was changed, in version 23.1 of Emacs.