Common Cron Schedule Examples

Cron is the Unix job scheduler that has been running scheduled tasks on servers since 1975, and the five-field cron expression syntax it invented has become the universal language for describing recurring schedules. Cloud schedulers (AWS EventBridge, Google Cloud Scheduler), CI/CD systems (GitHub Actions, GitLab CI), container orchestrators (Kubernetes CronJobs), and monitoring tools all use cron syntax. Learning the ten most common patterns covers the vast majority of real-world scheduling needs. The five fields in a standard cron expression are, from left to right: minute (0-59), hour (0-23), day of month (1-31), month (1-12), and day of week (0-7, where both 0 and 7 mean Sunday). An asterisk * in any field means "every valid value" for that field. Reading from left to right: "* * * * *" means "every minute of every hour of every day of every month on every day of the week" — the maximum frequency cron supports. The ten expressions in this example cover: every minute (* * * * *), every hour at the top of the hour (0 * * * *), daily at 9 AM (0 9 * * *), weekdays at 9 AM (0 9 * * 1-5), weekly on Sunday midnight (0 0 * * 0), monthly on the first at midnight (0 0 1 * *), once a year on January 1st (0 0 1 1 *), every 15 minutes (*/15 * * * *), every 6 hours (0 */6 * * *), and Monday mornings at 8:30 (30 8 * * 1). The slash notation (*/15) means "every N units of this field." */15 in the minute field creates four executions per hour at :00, :15, :30, and :45. This is distinct from 0,15,30,45 * * * * which is explicitly listing the same minutes — both produce the same schedule, but the slash notation is more concise. Common scheduling pitfalls: scheduling multiple jobs at exactly midnight or the top of the hour causes "thundering herd" problems where many jobs compete for system resources simultaneously. Stagger schedules by a few minutes (use :05, :10, :15 instead of :00 for all jobs) to spread the load. Also be aware that server timezone affects when cron fires — a job scheduled for 9:00 AM fires at different absolute times depending on the server's timezone setting. Cloud scheduler note: AWS EventBridge and Google Cloud Scheduler support timezone specification in the schedule configuration, which eliminates daylight saving time ambiguity. Traditional cron on a server uses the server's local timezone, which means schedules near the DST boundary may fire twice or be skipped during clock changes.

* * * * *
0 * * * *
0 9 * * *
0 9 * * 1-5
0 0 * * 0
0 0 1 * *
0 0 1 1 *
*/15 * * * *
0 */6 * * *
30 8 * * 1