How cron expressions work
A standard cron expression has five fields, in order: minute (0–59), hour (0–23), day of month (1–31), month (1–12), and day of week (0–6, Sunday first). An asterisk means "every". So 0 9 * * 1 means: at minute 0 of hour 9, any day of the month, any month, on Mondays — in other words, every Monday at 9:00 AM.
Common examples
Every minute: * * * * * — Every day at midnight: 0 0 * * * — Every 15th of the month at 6 AM: 0 6 15 * * — Weekdays at 8:30 AM: 30 8 * * 1-5 (this generator covers single values; ranges like 1-5 can be typed manually into your crontab).
Where cron is used
Cron schedules power Linux crontab, GitHub Actions schedules, Kubernetes CronJobs, cloud schedulers on GCP and AWS, and most CI/CD pipelines. The same five-field syntax works across nearly all of them.