Cron Expressions Explained: Schedule Like a Pro

Cron is the backbone of scheduled tasks on Unix systems and in cloud platforms like AWS EventBridge, GitHub Actions, and Kubernetes CronJobs. The expression syntax is compact but takes a moment to internalize.

The five fields

┌───── minute (0-59)
│ ┌─── hour (0-23)
│ │ ┌─ day of month (1-31)
│ │ │ ┌ month (1-12)
│ │ │ │ ┌ day of week (0-7, 0 and 7 = Sunday)
│ │ │ │ │
* * * * *

Special characters

• * — every value
• */n — every nth value (*/15 in minutes = every 15 min)
• a,b — specific values (1,15 = 1st and 15th)
• a-b — range (9-17 = 9am to 5pm)

Common examples

• 0 9 * * 1-5 — 9am weekdays
• */5 * * * * — every 5 minutes
• 0 0 1 * * — midnight on the 1st of every month
• 30 18 * * 5 — 6:30pm every Friday

Watch out for timezones

Cron traditionally runs in the server's local timezone. Cloud schedulers often default to UTC. Always check which timezone your cron runner uses.

Parse and describe any cron expression in plain English with ByteForge's Cron Parser.