AWS EventBridge Cron Expression Guide — Schedule Lambda and Events
Table of Contents
AWS EventBridge Scheduler (formerly CloudWatch Events) uses a cron format that's similar to standard cron — but with two key differences: a 6th field for year, and the ? character required in either day-of-month or day-of-week. Our free cron generator builds standard 5-field expressions that you can convert to AWS format using the patterns below.
AWS EventBridge Cron Format
AWS cron expressions have 6 fields:
cron(minutes hours day-of-month month day-of-week year)
Example: cron(0 9 ? * MON-FRI *) runs at 9 AM UTC on weekdays every year.
Key differences from standard Unix cron:
- Year field: Appended as the 6th field. Use
*for "every year" - Question mark (?): Required in either day-of-month or day-of-week when you specify the other. Cannot specify both.
- Starts at minute, not second: Unlike Quartz, AWS cron starts with minutes (same as standard cron). The year field is added at the end.
- Day of week: AWS uses 1=Sunday through 7=Saturday (Quartz-style), unlike Unix cron's 0=Sunday through 6=Saturday.
Common AWS EventBridge Cron Expressions
| Schedule | AWS Cron Expression |
|---|---|
| Every minute | cron(* * * * ? *) |
| Every 5 minutes | cron(0/5 * * * ? *) |
| Every hour | cron(0 * * * ? *) |
| Daily at midnight UTC | cron(0 0 * * ? *) |
| Daily at 9 AM UTC | cron(0 9 * * ? *) |
| Weekdays at 9 AM UTC | cron(0 9 ? * MON-FRI *) |
| First of month midnight | cron(0 0 1 * ? *) |
| Last day of month | cron(0 0 L * ? *) |
| Weekly Sunday midnight | cron(0 0 ? * SUN *) |
AWS Rate Expressions — Simpler Alternative to Cron
For simple intervals (every N minutes, hours, or days), AWS EventBridge also accepts rate expressions — much simpler than cron syntax:
rate(5 minutes) # Every 5 minutes rate(1 hour) # Every hour rate(24 hours) # Every 24 hours rate(7 days) # Every 7 days
Use rate expressions when you need a fixed interval without concern for exact clock time. Use cron expressions when you need to run at a specific time of day (like 9 AM) or on specific days (like weekdays or the 1st of the month).
Converting Standard Cron to AWS EventBridge Format
To convert a standard 5-field cron expression to AWS format:
- Take your standard expression:
0 9 * * 1-5 - Replace
*in the day-of-month field with?since day-of-week is specified:0 9 ? * 1-5 - Add a year field at the end:
0 9 ? * MON-FRI * - Wrap in
cron():cron(0 9 ? * MON-FRI *)
AWS uses day-of-week names (MON, TUE, WED, THU, FRI, SAT, SUN) rather than numbers, which actually makes the expressions more readable. Numbers also work: AWS uses 1-7 where 1=Sunday.
All AWS EventBridge cron jobs run in UTC. There's no timezone parameter — you need to calculate the UTC equivalent of your desired local time.
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Open Free Cron GeneratorFrequently Asked Questions
Does AWS EventBridge cron use UTC?
Yes, all AWS EventBridge scheduled rules run in UTC. There is no timezone parameter. To run a Lambda at 9 AM Eastern, schedule it at 14:00 UTC in winter (EST) and 13:00 UTC in summer (EDT).
Why does AWS cron require a question mark (?)?
AWS cron requires ? in either day-of-month or day-of-week to avoid ambiguity when specifying both fields. If you specify weekdays (like MON-FRI), day-of-month must be ? If you specify a specific date (like 1 for the 1st), day-of-week must be ?.
What is the difference between AWS rate() and cron() expressions?
Rate expressions (rate(5 minutes), rate(1 hour)) specify a fixed interval between runs. Cron expressions (cron(0 9 ? * MON-FRI *)) specify exact times. Use rate for simple intervals, cron for time-of-day or day-of-week specific scheduling.