Countdown timer that loops?

I’m trying to set up a site that has a timer theme based to it, where new deals are posted every six hours. I managed to get the posting part working but now I need a timer that runs for 6 hours and then starts the countdown all over again. I’ve found tons of countdowns and tried some but non of them loops and start over..they seem to have a mandatory end date. I pretty much want this thing to countdown from 6 hours to zero and back again forever. Any help would be appreciated.