Set margin only for desired modes! Do not frustrate calendar any more. Also set margin to 4 lines as continent see more next strings. My grouped lists of modes was placed at top. Do not change default-major-mode from fundamental-mode. When it was set to text-mode text-mode-hook have affect on calendar mode and when margin was set in hook it also set in calendar.

;; -*- mode: lisp; coding: utf-8 -*-
;;
;; For loading order see README.