elisp last monday date

lastmonday.el

(defun muihlinn-last-monday()
  "Date of last monday."

  (let* ( (date  (calendar-current-date))
          (today (calendar-absolute-from-gregorian date))
          (dow   (calendar-day-of-week date)))

    (cl-destructuring-bind (month day year)
      (calendar-gregorian-from-absolute
        ;; if sunday and our weeks starts on monday
        (if (and (eq dow 0) (eq calendar-week-start-day 1))
          (- today 6)
          (1+ (- today dow))))
      (format "%04d-%02d-%02d" year month day))))