# systemd Timers
Confidence: high
Last verified: 2026-05-22
Generation: human_only


## TL;DR

systemd timers are the modern replacement for cron, providing calendar and monotonic event scheduling with better logging, randomization, and dependency management. Timer unit triggers a matching service unit. `systemctl list-timers` shows all active timers.

## Core Explanation

Timer types: OnCalendar (specific times, like cron: `*-*-* 02:00:00` = daily 2AM), OnBootSec (after boot), OnUnitActiveSec (after service last ran). `RandomizedDelaySec` spreads load (avoid thundering herd). Persistent: `Persistent=true` catches up missed runs (like anacron). Accuracy: `AccuracySec` trades precision for power saving (default 1min).

## Further Reading

- [systemd.timer Documentation](undefined)