If you’ve been using Quartz.NET for background job scheduling, you’ve likely encountered the power and flexibility of cron expressions. They let you describe when a job should run using a compact, human‑readable syntax. Whether you’re new to cron or looking to deepen your understanding, this guide covers everything you need—syntax breakdown, over 20 practical examples, common pitfalls, how to test cron expressions, and a quick comparison with the SimpleTrigger.