entr - Run arbitrary commands when files change
Anacron - Anacron is a periodic command scheduler. It executes commands at intervals specified in days.
incron - This program is an "inotify cron" system. It consists of a daemon and a table manipulator.
fcron - Fcron is a scheduler designed for Unix/Linux systems, especially usefull when your system is not up all the day long.
mcron - mcron is GNU's implementation of cron. It is a 100% compatible replacement for Vixie cron.
System Scheduler - System Scheduler for Windows, Free Task Scheduler Software replace Microsoft Windows Task Scheduler