The new kids on the block, and another component that systemd brought into its gargantuan self, are systemd timers. Timers are another type of unit, only one that acts as the instruction for when another unit is to trigger.
In the old world, you'd control periodic events on a system with cron, and this is still widely used, but increasingly systemd timers are stealing that mantle away.
I say new but new is relative. Basically something can be in systemd for years before it finally trickles into Debian or CentOS. If you want the latest and greatest, run something like Fedora on a laptop.
In this section, we're going to look at existing cron and timer entries on our system, before converting our Python server into a timer-triggered service.