Re: Emacs Calendar - Removing holidays

[Jean Louis]

I understand you wish to highlight those days by your choice but not
holidays when you press `x', is it so?

Then maybe you do not need to erase holidays, you could maybe make a
function to mark those days you wish to mark and you can bind it to
any other key or even to `x'.

Holidays are in the list:

(((10 3 2020) "Sukkot") ((10 10 2020) "Shemini Atzeret") ((10 11 2020) "Simchat 
Torah") ((10 12 2020) "Columbus Day") ((10 20 2020) "Birth of the Báb") ((10 31 
2020) "Halloween") ((11 11 2020) "Veteran's Day") ((11 12 2020) "Birth of 
Bahá’u’lláh") ((11 26 2020) "Thanksgiving") ((12 11 2020) "Hanukkah") ((12 21 
2020) "Summer Solstice 1:02pm (EAT)") ((12 25 2020) "Christmas"))

One holiday is in this form:

((10 3 2020) "Sukkot")

So you could construct your list of holidays this way:

'((10 3 2020) "Sukkot")
  (11 29 2020) "Something else"))

And you put it in some function that returns such list or you can
simply construct that list and call it `my-important-dates'

Then copy this function `calendar-mark-holidays' to your file from holidays.el

(defun calendar-mark-holidays (&optional event)
  "Mark notable days in the calendar window.
If EVENT is non-nil, it's an event indicating the buffer position to
use instead of point."
  (interactive (list last-nonmenu-event))
  ;; If called from a menu, with the calendar window not selected.
  (with-current-buffer
      (if event (window-buffer (posn-window (event-start event)))
        (current-buffer))
    (setq calendar-mark-holidays-flag t)
    (message "Marking holidays...")
    (dolist (holiday (calendar-holiday-list))
      (calendar-mark-visible-date (car holiday) calendar-holiday-marker))
    (message "Marking holidays...done")))

Then change it little by:

(defun my-calendar-mark-my-days (&optional event)
  "Mark notable days in the calendar window.
  (interactive)
  ;; If called from a menu, with the calendar window not selected.
  (with-current-buffer
    (setq calendar-mark-holidays-flag t)
    (message "Marking my days...")
    (dolist (holiday (this-function-returns-my-days))
      (calendar-mark-visible-date (car holiday) calendar-holiday-marker))
    (message "Marking my days...done")))

Then you may bind that function to a key in calendar mode map.