Cron is the classic Unix job scheduler, and its schedule syntax has spread far beyond it: CI pipelines, cloud schedulers, and job queues all accept cron expressions. The syntax is compact, which makes it easy to get subtly wrong. Here is how to read and write it with confidence.
Source: [Dev.to](https://dev.to/pulkitgovrani/what-a-cron-expression-actually-means-with-examples-4kcl)