Cron Expression Guide: Schedule Jobs Like a Pro

What is a Cron Expression?

A cron expression is a string of five (or six) fields that define a schedule for recurring tasks. Cron is the time-based job scheduler in Unix-like systems. The name comes from the Greek word "chronos" (time).

┌───── minute (0-59) │ ┌─── hour (0-23) │ │ ┌─ day of month (1-31) │ │ │ ┌ month (1-12) │ │ │ │ ┌ day of week (0-6, Sunday=0) │ │ │ │ │ * * * * *

Special Characters

Character	Meaning	Example
`*`	Any value	`* * * * *` — every minute
`,`	List separator	`1,15,30` — at minutes 1, 15, and 30
`-`	Range	`9-17` — hours 9 through 17
`/`	Step values	`*/15` — every 15 units

Common Patterns

Expression	Meaning
`* * * * *`	Every minute
`0 * * * *`	Every hour (at :00)
`0 0 * * *`	Every day at midnight
`0 0 * * 0`	Every Sunday at midnight
`0 9 * * 1-5`	Every weekday at 9:00 AM
`0 0 1 * *`	First day of every month at midnight
`0 0 1 1 *`	January 1st at midnight (yearly)
`/15 * * *`	Every 15 minutes
`0 9,12,18 * * *`	At 9:00, 12:00, and 18:00 daily
`0 0 * * 1`	Every Monday at midnight

Cron in Different Environments

Linux Crontab

# Edit crontab
crontab -e

# Backup database every day at 2 AM
0 2 * * * /scripts/backup-db.sh

# Clean temp files every Sunday at 3 AM
0 3 * * 0 /scripts/cleanup.sh

AWS EventBridge (CloudWatch Events)

AWS uses a 6-field cron with year field: cron(Minutes Hours Day Month Weekday Year)

# Every day at 10 AM UTC
cron(0 10 * * ? *)

# Every weekday at 8 AM
cron(0 8 ? * MON-FRI *)

Kubernetes CronJob

apiVersion: batch/v1
kind: CronJob
spec:
  schedule: "0 2 * * *"  # Every day at 2 AM

✓ Tip: Always test cron expressions before deploying to production. Use the FreeUtil Cron Builder to preview the next 8 run times and verify your expression does what you expect.