(defun my/magit-diff-since (&optional since)
  "Shows the diff for the current file SINCE the given date/time."
  (interactive "sSince (default 24 hours ago): ")
  (let* ((revisionA (format "HEAD@{%s}" (or (and (not (string-empty-p since)) since) "24 hours ago")))
         (revisionB "{worktree}")
         (range (string-join (list revisionA ".." revisionB))))
    (magit-diff-range range () (list (buffer-file-name)))))