Overview

Cron Expressions Course

Learn Unix cron syntax: five fields, ranges and steps, timezone traps, platform differences, common job patterns, and a practical debugging workflow.

This course teaches Unix cron as a scheduling language—not as a walkthrough of a parser UI. You will learn the five-field format, how wildcards and steps combine, why timezones break assumptions across platforms, and how to verify a schedule before it wakes someone at 3 a.m.

Who this course is for

  • Developers writing crontab lines, Kubernetes CronJob specs, or CI schedules
  • SRE and platform engineers reviewing backup and cleanup jobs
  • Anyone who pasted 0 0 * * * and hoped it meant what they thought

What you will learn

  1. What cron schedules and where five-field syntax is used
  2. Field order, bounds, *, lists, ranges, and / steps
  3. Timezone rules on Linux, Kubernetes, and GitHub Actions
  4. Patterns for hourly, weekday, weekly, and monthly jobs
  5. A debugging workflow with human-readable descriptions and next-run previews

Use the related Cron Expression Parser to test examples locally. A valid expression in one platform’s timezone is not necessarily the same instant in another.

Start lesson 1
Cron on Kubernetes vs Linux Crontab: Timezone TrapsWhy the same five-field cron string fires at different times on GitHub Actions, K8s CronJob, and server crontab—and how to preview safely.