Anacron is a periodic command scheduler. It executes commands at intervals specified in days. Unlike cron, it does not assume that the system is running continuously. It can therefore be used to control the execution of daily, weekly, and monthly jobs (or anything with a period of n days), on systems that don't run 24 hours a day. When installed and configured properly, Anacron will make sure that the commands are run at the specified intervals as closely as machine-uptime permits.
Release Notes: first freshmeat announcement