AWS

Cron Expressions for AWS EventBridge Scheduler

AWS EventBridge (formerly CloudWatch Events) uses a 6-field cron syntax that adds a 'year' field. It also requires '?' in either the day-of-month or day-of-week field — you cannot specify both. All schedules run in UTC.

Format

6-field cron

Fields

6 fields: minute hour day-of-month month day-of-week year

Timezone

UTC (fixed)

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Common EventBridge Cron Patterns

Every 5 minutes

0/5 * * * ? *

Runs every 5 minutes (use 0/5 not */5 in EventBridge)

Use caseLambda polling, health checks

Every hour

0 * * * ? *

Runs at the top of every hour

Use caseHourly Lambda trigger, batch processing

Daily at noon UTC

0 12 * * ? *

Runs every day at 12:00 UTC

Use caseMidday report generation, Lambda invocation

Weekdays at 8am UTC

0 8 ? * MON-FRI *

Runs Monday through Friday at 08:00 UTC

Use caseBusiness-hours automation, workday start tasks

Every Monday

0 0 ? * 2 *

Runs every Monday at midnight UTC (2=Monday in EventBridge)

Use caseWeekly jobs, scheduled audits

First of every month

0 0 1 * ? *

Runs at midnight UTC on the 1st

Use caseMonthly invoices, SLO snapshots

Last day of month

0 23 L * ? *

Runs at 23:00 UTC on the last day of every month

Use caseEnd-of-month reporting, data archival

Specific year

0 0 1 1 ? 2027

Runs once on January 1st, 2027 at midnight

Use caseOne-time scheduled task, data migration

AWS EventBridge Rule — Cron Schedule

yamlEventBridge

# AWS CloudFormation template
Resources:
  ScheduledRule:
    Type: AWS::Events::Rule
    Properties:
      Description: "Run Lambda every day at noon UTC"
      ScheduleExpression: "cron(0 12 * * ? *)"
      State: ENABLED
      Targets:
        - Arn: !GetAtt MyFunction.Arn
          Id: "TargetFunctionV1"

  # Permission for EventBridge to invoke Lambda
  PermissionForEventsToInvokeLambda:
    Type: AWS::Lambda::Permission
    Properties:
      FunctionName: !Ref MyFunction
      Action: "lambda:InvokeFunction"
      Principal: "events.amazonaws.com"
      SourceArn: !GetAtt ScheduledRule.Arn

How EventBridge Differs from Standard Crontab

EventBridge adds a 6th 'year' field and requires '?' for day-of-month or day-of-week. Step values use '0/n' instead of '*/n'. Day-of-week numbering starts at 1 (Sunday), not 0. The entire expression must be wrapped in 'cron(...)'.

Common Gotchas & Pitfalls

The '?' wildcard is required — use '?' for either day-of-month OR day-of-week (not both).

Use '0/5' instead of '*/5' for step values — EventBridge does not support the '*/n' syntax.

Day-of-week uses different numbering: SUN=1, MON=2, TUE=3, WED=4, THU=5, FRI=6, SAT=7 (or use 3-letter abbreviations).

The expression must be wrapped in 'cron(...)' when using the console or CloudFormation.

AWS EventBridge also supports 'rate(5 minutes)' expressions as an alternative to cron.

The year field can be a specific year (2025), a range (2025-2027), or '*' for any year.

Minimum schedule rate is 1 minute; the 'every second' frequency is not supported.

Other Platform Guides

GitHub Actions Kubernetes GCP Scheduler Azure Functions

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