Cron Expression Explainer

Cron syntax cheat sheet

┌───────────── minute (0–59)
│ ┌─────────── hour (0–23)
│ │ ┌───────── day of month (1–31)
│ │ │ ┌─────── month (1–12 or JAN–DEC)
│ │ │ │ ┌───── day of week (0–7 or SUN–SAT, 0 and 7 = Sunday)
│ │ │ │ │
* * * * *  command

Gotchas

• Day-of-month OR day-of-week: if both fields are restricted, cron runs when either matches. 0 0 13 * 5 runs on every 13th and every Friday.
• Timezone: cron uses the server's timezone (check with timedatectl). Kubernetes CronJobs support spec.timeZone.
• Environment: cron runs with a minimal PATH. Use absolute paths and redirect output to a log.
• Overlap: wrap long jobs with flock -n /tmp/job.lock so runs don't pile up.

Common schedules

• Every minute * * * * *
• Every 2 minutes */2 * * * *
• Every 5 minutes */5 * * * *
• Every 10 minutes */10 * * * *
• Every 15 minutes */15 * * * *
• Every 30 minutes */30 * * * *
• Every hour 0 * * * *
• Every 2 hours 0 */2 * * *
• Every 6 hours 0 */6 * * *
• Every 12 hours 0 */12 * * *
• Every day at midnight 0 0 * * *
• Every day at 2 AM 0 2 * * *
• Every weekday at 9 AM 0 9 * * 1-5
• Every Saturday and Sunday 0 0 * * 6,0
• Every Monday 0 0 * * 1
• Every Sunday 0 0 * * 0
• First day of every month 0 0 1 * *
• Every quarter 0 0 1 1,4,7,10 *
• Once a year 0 0 1 1 *
• Every 15 minutes during business hours */15 9-17 * * 1-5