ruiyun.tools.timer is an easy to use Java Timer wrapper for clojure.
You can simply start a period task in every 5 seconds immediately like this:

  (run-task! #(println "Say hello every 5 seconds.") :period 5000)

If you want delay the first run with 2 seconds：

  (run-task! #(println "Say hello after 2 seconds.") :dealy 2000)

Use this if you want to execute a task at an absolute time：

  (run-task! #(println "Say hello at 2013-01-01T00:00:00 in beijing.") :at #inst "2013-01-01T00:00:00+08:00")

And, you can use the same timer in more than one tasks:

  (def greeting-timer (timer "The timer for greeting"))
  (run-task! #(println "Say hello after 2 seconds.") :dealy 2000 :by greeting-timer)
  (run-task! #(println "Say hello every 5 seconds.") :period 5000 :by greeting-timer)

Finally, you can cancel a timer's tasks:

  (cancel! greeting-timer)