Cron Expression Guide: Schedule Any Job in 5 Minutes

Cron syntax looks like someone smashed their keyboard: */5 * * * *. But it's actually simple once you understand the five fields.

The Five Fields

* * * * *
| | | | |
| | | | +-- Day of week (0-7, 0 and 7 = Sunday)
| | | +---- Month (1-12)
| | +------ Day of month (1-31)
| +-------- Hour (0-23)
+---------- Minute (0-59)

Common Schedules

• * * * * * - Every minute
• */5 * * * * - Every 5 minutes
• 0 * * * * - Every hour (at minute 0)
• 0 9 * * * - Every day at 9:00 AM
• 0 9 * * 1 - Every Monday at 9:00 AM
• 0 0 1 * * - First day of every month at midnight
• 0 9 * * 1-5 - Weekdays at 9:00 AM

Build and Test Expressions

The Cron Builder lets you construct expressions visually and see the next 10 execution times. No more guessing if your expression is right. Build it, verify the schedule, copy the expression.

Gotchas

Timezone: Cron runs in the server's timezone unless you specify otherwise. If your server is in UTC and you want 9 AM Eastern, that's 0 14 * * * in summer (EDT) and 0 13 * * * in winter (EST). Or just set TZ in your cron environment.

Overlapping runs: If your job takes 10 minutes and runs every 5, you'll have overlapping instances. Add a lock file or use flock.