Anacron runs the periodic daily, weekly and monthly tasks on your Mac even if the machine (a laptop, for example) spends much of its time asleep or switched-off. Anacron silently checks when you reboot and every sixty minutes while the computer is running to see if the various periodic scripts are overdue, and runs them if necessary. The advantage of Anacron over many other solutions to this issue is that it runs as a proper Unix background process, requires no user intervention, and uses the regular periodic scripts, including local additions or modifications.