(defun xah-insert-date ()
"Insert current date time.
Insert date in this format: yyyy-mm-dd.
If `universal-argument' is called first, prompt for a format to use.
If there is selection, delete it first.

URL `http://xahlee.info/emacs/emacs/elisp_insert-date-time.html'
Created: 2013-05-10
Version: 2025-03-07"
(interactive)
(let (xmenu xstyle)
(setq
xmenu
'(("ISO date • 2018-04-12" . (format-time-string "%Y-%m-%d"))
("all digits datetime • 20180412224611" . (format-time-string "%Y%m%d%H%M%S"))
("date _ time digits • 2018-04-12_224611" . (format-time-string "%Y-%m-%d_%H%M%S"))
("ISO datetime full • 2018-04-12T22:46:11-07:00" .
(concat
(format-time-string "%Y-%m-%dT%T")
(funcall (lambda (xx) (format "%s:%s" (substring xx 0 3) (substring xx 3 5)))
(format-time-string "%z"))))
("ISO datetime w space • 2018-04-12 22:46:11-07:00" .
(concat
(format-time-string "%Y-%m-%d %T")
(funcall
(lambda (xx) (format "%s:%s" (substring xx 0 3) (substring xx 3 5)))
(format-time-string "%z"))))
("ISO date + weekday • 2018-04-12 Thursday" . (format-time-string "%Y-%m-%d %A"))
("USA date + weekday • Thursday, April 12, 2018" . (format-time-string "%A, %B %d, %Y"))
("USA date + weekday abbrev • Thu, Apr 12, 2018" . (format-time-string "%a, %b %d, %Y"))
("USA date • April 12, 2018" . (format-time-string "%B %d, %Y"))
("USA date abbrev • Apr 12, 2018" . (format-time-string "%b %d, %Y")))

xstyle
(if current-prefix-arg
(let ((completion-ignore-case t))
(completing-read "Style:" xmenu nil t nil nil (caar xmenu)))
(caar xmenu)))
(when (region-active-p) (delete-region (region-beginning) (region-end)))
(insert (eval (cdr (assoc xstyle xmenu))))))

(defun xah-insert-date ()
  "Insert current date time.
Insert date in this format: yyyy-mm-dd.
If `universal-argument' is called first, prompt for a format to use.
If there is selection, delete it first.

URL `http://xahlee.info/emacs/emacs/elisp_insert-date-time.html'
Created: 2013-05-10
Version: 2025-03-07"
  (interactive)
  (let (xmenu xstyle)
    (setq
     xmenu
     '(("ISO date • 2018-04-12" . (format-time-string "%Y-%m-%d"))
       ("all digits datetime • 20180412224611" . (format-time-string "%Y%m%d%H%M%S"))
       ("date _ time digits • 2018-04-12_224611" . (format-time-string "%Y-%m-%d_%H%M%S"))
       ("ISO datetime full • 2018-04-12T22:46:11-07:00" .
        (concat
         (format-time-string "%Y-%m-%dT%T")
         (funcall (lambda (xx) (format "%s:%s" (substring xx 0 3) (substring xx 3 5)))
                  (format-time-string "%z"))))
       ("ISO datetime w space • 2018-04-12 22:46:11-07:00" .
        (concat
         (format-time-string "%Y-%m-%d %T")
         (funcall
          (lambda (xx) (format "%s:%s" (substring xx 0 3) (substring xx 3 5)))
          (format-time-string "%z"))))
       ("ISO date + weekday • 2018-04-12 Thursday" . (format-time-string "%Y-%m-%d %A"))
       ("USA date + weekday • Thursday, April 12, 2018" . (format-time-string "%A, %B %d, %Y"))
       ("USA date + weekday abbrev • Thu, Apr 12, 2018" . (format-time-string "%a, %b %d, %Y"))
       ("USA date • April 12, 2018" . (format-time-string "%B %d, %Y"))
       ("USA date abbrev • Apr 12, 2018" . (format-time-string "%b %d, %Y")))

     xstyle
     (if current-prefix-arg
         (let ((completion-ignore-case t))
           (completing-read "Style:" xmenu nil t nil nil (caar xmenu)))
       (caar xmenu)))
    (when (region-active-p) (delete-region (region-beginning) (region-end)))
    (insert (eval (cdr (assoc xstyle xmenu))))))

(defun xah-make-backup ()
  "Make a backup copy of current file or dired marked files.
If in dired, backup current file or marked files.
The backup file name is in this format
 x.html~2018-05-15_133429~
The last part is hour, minutes, seconds.

Overwrite existing file.

If the current buffer is not associated with a file, nothing's done.

URL `http://xahlee.info/emacs/emacs/elisp_make-backup.html'
Created: 2018-07-07
Version: 2024-04-21"
  (interactive)
  (let ((xfname buffer-file-name)
        (xdateTimeFormat "%Y-%m-%d_%H%M%S"))
    (if xfname
        (let ((xbackupName
               (concat xfname "~" (format-time-string xdateTimeFormat) "~")))
          (copy-file xfname xbackupName t)
          (message (concat "\nBackup saved at: " xbackupName)))
      (if (eq major-mode 'dired-mode)
          (progn
            (mapc (lambda (xx)
                    (let ((xbackupName
                           (concat xx "~" (format-time-string xdateTimeFormat) "~")))
                      (copy-file xx xbackupName t)))
                  (dired-get-marked-files))
            (revert-buffer))
        (user-error "%s: buffer not file nor dired" real-this-command)))))

(defun xah-toggle-letter-case ()
  "Toggle the letter case of current word or selection.
Always cycle in this order: Init Caps, ALL CAPS, all lower.

URL `http://xahlee.info/emacs/emacs/emacs_toggle_letter_case.html'
Version: 2020-06-26 2023-11-14"
  (interactive)
  (let ( (deactivate-mark nil) xp1 xp2)
    (if (region-active-p)
        (setq xp1 (region-beginning) xp2 (region-end))
      (save-excursion
        (skip-chars-backward "[:alpha:]")
        (setq xp1 (point))
        (skip-chars-forward "[:alpha:]")
        (setq xp2 (point))))
    (when (not (eq last-command this-command))
      (put this-command 'state 0))
    (cond
     ((equal 0 (get this-command 'state))
      (upcase-initials-region xp1 xp2)
      (put this-command 'state 1))
     ((equal 1 (get this-command 'state))
      (upcase-region xp1 xp2)
      (put this-command 'state 2))
     ((equal 2 (get this-command 'state))
      (downcase-region xp1 xp2)
      (put this-command 'state 0)))))Language:Clojure