Scheduled Task

I would suggest using a backup utility that has scheduling capabilities. A couple of possible choices would be Carbon Copy Cloner and SilverKeeper - VersionTracker or MacUpdate.

If you know how to write a shell script or an AppleScript then you can use the cron facility of OS X. To see how cron is used open the Terminal application in your Utilities folder and enter: man cron to get the doc pages on its usage.

you can make an automator workflow to copy the folder. there are various ways to schedule its execution. you can save the workflow as an ical plugin and make a recurring ical event with the alarm set to run the workflow. or you can set up a cron (use Cronnix) or a launch daemon (use Lingon) to run the workflow on a schedule you want. However, for this kind of task i would simply recommend one of the myriad 3rd party folder sync apps like Chronosync. any one will do what you want. search MacUpdate for more options.