CRON Expressions for AWS CloudWatch Events
Generate CRON expressions for AWS CloudWatch Events (EventBridge) rules. Create schedules to trigger Lambda functions, EC2 actions, or other AWS services automatically.
AWS CloudWatch Cron Generator
Generate cron expressions for AWS CloudWatch
How to use
Enter your data in the input field, click Convert, and the result will appear in the output field. You can then copy or download the result.
How AWS CloudWatch Events Cron Expressions Work
This tool generates and validates cron expressions specifically for AWS CloudWatch Events (EventBridge). AWS uses a slightly different cron format than standard Unix cron - understanding the differences ensures your scheduled events trigger correctly.
AWS cron expressions have 6 fields: Minute, Hour, Day-of-month, Month, Day-of-week, and Year. The Year field is unique to AWS - standard cron doesn't have it. AWS also uses different special characters and has specific rules for wildcards.
AWS cron expression format:
- Minute: 0-59
- Hour: 0-23
- Day-of-month: 1-31
- Month: 1-12 or JAN-DEC
- Day-of-week: 1-7 or SUN-SAT (1=Sunday)
- Year: 1970-2199
Common use cases include running Lambda functions on schedules, triggering ECS tasks, automating backups, and periodic data processing. The generator helps you create correct expressions for these scenarios.
When You'd Actually Use This
Scheduling Lambda functions
Need to run a Lambda every day at 3 AM UTC? Generate the cron expression: cron(0 3 * * ? *). Use in EventBridge rule to trigger your function automatically.
Automating RDS snapshots
Schedule automated database backups. Create snapshots every 6 hours: cron(0 0/6 ? * * *). Ensures point-in-time recovery options throughout the day.
Running periodic data exports
Export data to S3 every Monday at 6 AM: cron(0 6 ? * MON *). Weekly reports, data warehouse syncs, and compliance exports all use scheduled events.
Cleanup and maintenance tasks
Delete old temp files on 1st of each month: cron(0 0 1 * ? *). Automated cleanup prevents storage bloat and reduces costs.
Business hours notifications
Send daily digest at 9 AM on weekdays only: cron(0 9 ? * MON-FRI *). Weekend suppression ensures no unnecessary notifications.
End-of-month processing
Run billing calculations on last day of month: cron(0 23 L * ? *). The 'L' wildcard means last day of month, handling 28-31 day variations automatically.
What to Know Before Using
AWS uses ? for either day field.You can't specify both Day-of-month and Day-of-week. Use ? in one field when specifying the other. cron(0 0 1 * ? *) (1st of month) not cron(0 0 1 * 1 *).
Day-of-week: 1=Sunday in AWS.Unlike some systems where 1=Monday, AWS uses 1=Sunday, 7=Saturday. This trips up many users. Use SUN-SAT names for clarity.
Year field is required.Standard cron has 5 fields, AWS has 6. Don't forget the Year field. Use * for every year, or specify a range like 2024-2025.
Timezone is UTC only.CloudWatch Events always use UTC. A 9 AM schedule runs at 9 AM UTC, not your local time. Convert your local time to UTC for the expression.
Pro tip: Test cron expressions in the EventBridge console before deploying. Use "Matched events" to verify your expression triggers at expected times.
Common Questions
What's the difference between AWS cron and Unix cron?
AWS has 6 fields (includes Year), Unix has 5. AWS uses ? for "no specific value". AWS day-of-week starts with 1=Sunday. AWS supports L (last) and W (nearest weekday) wildcards.
How do I run something every 5 minutes?
Use rate(5 minutes) instead of cron for sub-hour intervals. For cron: cron(0/5 * ? * * *) but rate expressions are simpler for this use case.
Can I schedule at specific times on specific days?
Yes. 9 AM on Mondays and Fridays: cron(0 9 ? * MON,FRI *). Multiple values use commas. Ranges use hyphens (MON-FRI).
What does the ? wildcard mean?
? means "no specific value". Use it in Day-of-month when you specify Day-of-week, or vice versa. You can't have specific values in both fields.
How do I run on the last day of each month?
Use L in Day-of-month field: cron(0 23 L * ? *) runs at 11 PM on the last day of every month. Works for 28, 29, 30, and 31 day months.
Can I use cron for one-time events?
Cron is for recurring schedules. For one-time events, use EventBridge scheduled events with a specific date/time, or use EventBridge Pipes with a schedule.
What timezone does AWS cron use?
Always UTC. There's no timezone field in AWS cron expressions. Convert your local time to UTC before creating the expression. Consider DST changes when scheduling.
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