AWS Cron Expression Builder

Free AWS EventBridge cron expression builder. AWS uses a 6-field cron format different from standard Linux cron — it adds a Seconds field, uses SUN–SAT for days, and requires ? instead of * in conflicting day fields. All times are UTC. This tool generates the correct AWS cron() syntax plus AWS CLI, CloudFormation, and Terraform code.

⚠️ AWS cron is NOT the same as Linux cron. AWS EventBridge uses a 6-field format: seconds minute hour day-of-month month day-of-week year. The standard crontab format has 5 fields (no seconds, no year). Always use cron() wrapper in AWS.

⚡ AWS Schedule Presets

🔧 AWS Cron Builder (6 fields)

Seconds

0-59 or *

Minute

0-59 or *

Hour

0-23 or *

Day/Month

1-31 or ?

Month

1-12 or *

Day/Week

SUN-SAT or ?

Year

* or 2024

cron(0 9 * * ? *)

✅ Runs every hour, on *, day * of month, in month ? (UTC)

📋 Ready-to-Use AWS Code

AWS CLI

aws events put-rule \
  --name "MyScheduledRule" \
  --schedule-expression "cron(0 9 * * ? *)" \
  --state ENABLED

# Attach a Lambda target:
aws events put-targets \
  --rule "MyScheduledRule" \
  --targets "Id=1,Arn=arn:aws:lambda:us-east-1:123456789:function:MyFunction"

CloudFormation

Resources:
  MyScheduledRule:
    Type: AWS::Events::Rule
    Properties:
      Name: MyScheduledRule
      ScheduleExpression: "cron(0 9 * * ? *)"
      State: ENABLED
      Targets:
        - Id: "MyLambdaTarget"
          Arn: !GetAtt MyLambdaFunction.Arn

Terraform

resource "aws_cloudwatch_event_rule" "schedule" {
  name                = "my-scheduled-rule"
  schedule_expression = "cron(0 9 * * ? *)"
}

resource "aws_cloudwatch_event_target" "lambda" {
  rule      = aws_cloudwatch_event_rule.schedule.name
  target_id = "lambda"
  arn       = aws_lambda_function.my_function.arn
}

🔍 AWS Cron vs Standard Cron — Key Differences

AWS EventBridge uses a 6-field variant of the Quartz cron format. If you copy a standard Linux cron expression directly into EventBridge, it will either reject it or run at the wrong time. Here are the critical differences:

Field	Standard cron	AWS EventBridge	Note
Seconds	— (not supported)	0–59 (first field)	AWS adds a Seconds field at position 1
Day of month	1–31 or *	1–31, * or ?	Use ? when specifying Day of Week
Day of week	0–6 (0=Sunday)	SUN–SAT or 1–7, use ?	AWS uses SUN/MON/TUE… not 0–6
Year	— (not supported)	1970–2199 or *	AWS adds a Year field at position 6
Step (every N)	*/5	0/5	AWS uses 0/N not */N

❓ AWS Cron FAQ

What is an AWS EventBridge cron expression?

An AWS cron expression is a 6-field schedule string used by EventBridge (formerly CloudWatch Events) to trigger AWS services like Lambda, Step Functions, and ECS tasks on a schedule. The format is: cron(seconds minute hour day-of-month month day-of-week year). Always wrap in cron() when using as a ScheduleExpression.

Why does AWS cron use ? instead of *?

AWS cron does not allow you to specify both day-of-month and day-of-week at the same time. Whichever you don't want to restrict, set to ? (no specific value). For example, to run every Monday: cron(0 9 ? * MON *) — the day-of-month is ? because you're specifying day-of-week.

Does AWS EventBridge cron support timezones?

EventBridge runs all cron schedules in UTC by default. AWS EventBridge Scheduler (the newer service) supports timezones. If you need IST (UTC+5:30), subtract 5 hours 30 minutes from your desired time when configuring standard EventBridge rules.

What is the minimum schedule interval for EventBridge?

EventBridge supports a minimum of 1 minute intervals using rate expressions (rate(1 minute)) or cron expressions. For sub-minute precision you need a different approach (Step Functions, SQS with visibility timeout, etc.).

How do I test an AWS cron expression before deploying?

Use this tool to see the next 8 run times in UTC. You can also use the AWS console — when creating an EventBridge rule, it shows the next 10 trigger times after you enter the schedule expression.