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AWS EventBridge cron expression format

AWS EventBridge (and CloudWatch Events) cron expressions have six fields and differ from five-field Unix cron: they add a year field, run in UTC, and require ? in one of the day fields.

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The problem

Pasting a Unix five-field cron into EventBridge fails, and so does using * in both the day-of-month and day-of-week fields at once. EventBridge fields are: minutes, hours, day-of-month, month, day-of-week, year. Exactly one of day-of-month or day-of-week must be ?.

All schedules are evaluated in UTC, not your local timezone.

Sample input

EventBridge expression
cron(0 9 ? * MON-FRI *)

Expected output

Meaning
09:00 UTC, Monday through Friday, every month, every year

Minutes 0, hours 9, day-of-month ? (unspecified because day-of-week is set), month *, day-of-week MON-FRI, year *.

How to do it

  1. Write the minute and hour in UTC.
  2. Set day-of-month, or use ? if you are scheduling by weekday.
  3. Set the month (* for every month).
  4. Set day-of-week, using ? here instead if you scheduled by day-of-month.
  5. Set the year, or * for every year.
  6. Validate the schedule and confirm the next run times.

Common mistakes

  • Using a five-field Unix cron expression in EventBridge.
  • Forgetting that EventBridge schedules run in UTC.
  • Putting a value in both day-of-month and day-of-week instead of using ? in one.
  • Omitting the year field.
  • Expecting local-timezone behavior.

Related tools

Related guides

FAQ

How many fields does AWS EventBridge cron use?

Six: minutes, hours, day-of-month, month, day-of-week, and year.

What does ? mean in AWS cron?

It marks the day-of-month or day-of-week field as unspecified. EventBridge requires exactly one of those two fields to be ? when the other is set.

Is AWS EventBridge cron UTC?

Yes. Cron-based EventBridge schedules are evaluated in UTC. (Newer EventBridge Scheduler can apply a timezone, but classic cron rules are UTC.)

Can I use 5-field cron in EventBridge?

No. EventBridge cron expressions must use the six-field format wrapped in cron(...).

How do I schedule weekdays only?

Use ? for day-of-month and MON-FRI for day-of-week, for example cron(0 9 ? * MON-FRI *).

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