Are you questioning yourself if you should use one or the other? Here we are going to reply to the questions you may no have asked yourself!

Cron is a time-based job scheduler. It is typically used to schedule repetitive tasks.

Systemd is a software suite for system and service management on Linux, built to unify service configuration and behavior across Linux distributions. Its main component is an init system used to bootstrap user space and manage user processes.

In other words, Cron is the classic Linux task scheduler. It is based on a configuration file, the crontab, which provides a list of jobs and the times they should run. It has a simple syntax, based on five-asterisk format, which represents minute, hour, day of the month, month, and day of the week.

Systemd timers, part of Systemd suite, is a more modern approach to scheduling. Instead of one file, they use two, a .service file, defining what to be run, and a .timer file, defining when to run the service.

Systemd offers moe scheduling options, like event-based triggers, dependency management, integrated logging, missed job handling, resource control.

So, why we should keep using Cron?

If you need a script to be run in non-systemd environments, or your task is extremely simple that its triggering conditions can be resumed by the crontab, or you need a simple crontab permission model to handle a multi-users environment, you should go for Cron.

If instead you need to run jobs following the boot, or you need more complex triggering rules, or you need to manage resources or failures, well, Systemd, even if more complex to handle, can simplif your job.

Conclusion

Cron is simple, predictable, and reliable. It has been working for decades, and will continue to be the first choice when you need to handle basic settings. But it is not really evolving, apart some notable updates, that anyway are not standard and not supported everywhere (e.g. the frequency settings).

If you will need to handle more complex dependencies, conditions, resources, Systemd is the solution to be considered.