Clon is a Common Lisp library for scheduling much like cron. It's under the MIT licence. See COPYING. How to use it: ;;; create a stateless schedule: (make-typed-cron-schedule :second '(member 0 10 20 30 40 50)) ;;; create a scheduler that remembers the last scheduled time: (make-scheduler *) ;;; schedule a function: (schedule-function (lambda () (print (get-universal-time))) *) ;;; unschedule the timer returned by SCHEDULE-FUNCTION: (trivial-timers:unschedule-timer *)