sysutils/anacron 2.5.3p5 OpenBSD

What it is: 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.

What it is not: Anacron is not an attempt to make cron redundant. It cannot be used to schedule commands at intervals smaller than days. It also does not guarantee that the commands will be executed at any specific day or hour. It isn't a full-time daemon. It has to be executed from boot scripts, from cron-jobs, or explicitly.