How does EventBridge cron differ from Unix cron?

EventBridge uses six fields (minute, hour, day-of-month, month, day-of-week, year) compared to Unix cron's five. Either day-of-month or day-of-week must be a question mark (?). EventBridge supports L (last), W (weekday), and # (nth day-of-week) modifiers. All times are in UTC.

What is the difference between cron and rate expressions?

Cron expressions define specific recurring schedules (e.g., 'cron(0 12 * * ? *)' for noon daily). Rate expressions define simple intervals (e.g., 'rate(5 minutes)' or 'rate(1 hour)'). Use cron for calendar-based schedules and rate for fixed-interval triggers.

Can I schedule in a specific timezone?

EventBridge Scheduler (the newer service) supports timezone-aware scheduling with the ScheduleExpressionTimezone parameter. Classic EventBridge rules always evaluate cron expressions in UTC. If using classic rules, adjust your cron expression to account for the UTC offset.

EventBridge Cron Builder

ServerlessAWS

Build and validate EventBridge cron and rate expressions with human-readable previews.

Expression Builder

Expression Type

Common Presets

Minutes

0-59, *, or increments like 0/5

Hours

0-23, *, or increments like 0/2

Day of Month

1-31, *, ?, L, or W (e.g. 15W)

Month

1-12, JAN-DEC, or *

Day of Week

1-7, SUN-SAT, ?, *, L, or # (e.g. MON#1)

Year

1970-2199 or *

Expression Preview

cron(0 * * * ? *)

Result

Validcron(0 * * * ? *)

at minute 0

Next Occurrences (approximate)

1. 2026-03-18T00:00:00.000Z
2. 2026-03-19T00:00:00.000Z
3. 2026-03-20T00:00:00.000Z
4. 2026-03-21T00:00:00.000Z
5. 2026-03-22T00:00:00.000Z

Parse Existing Expression

EventBridge Expression

Generated Expression

cron(0 * * * ? *)

Description: at minute 0

Next occurrences (approximate):
  1. 2026-03-18T00:00:00.000Z
  2. 2026-03-19T00:00:00.000Z
  3. 2026-03-20T00:00:00.000Z
  4. 2026-03-21T00:00:00.000Z
  5. 2026-03-22T00:00:00.000Z

About This Tool

The EventBridge Cron Builder helps you create and validate cron and rate expressions for Amazon EventBridge scheduled rules. EventBridge cron syntax differs from standard Unix cron in several ways, including the year field, the requirement that either day-of-month or day-of-week must be a question mark, and the use of L and W modifiers. The tool previews upcoming execution times and translates expressions into human-readable descriptions.

When to Use This Tool

•Building a schedule expression for an EventBridge rule that triggers a Lambda function on the last business day of each month.
•Validating that an EventBridge cron expression fires at the correct times across multiple days before deploying.
•Converting standard Unix cron expressions to EventBridge's six-field format with the question mark requirement.
•Creating rate expressions for simple periodic schedules like every 5 minutes or every 12 hours.

Frequently Asked Questions

How does EventBridge cron differ from Unix cron?: EventBridge uses six fields (minute, hour, day-of-month, month, day-of-week, year) compared to Unix cron's five. Either day-of-month or day-of-week must be a question mark (?). EventBridge supports L (last), W (weekday), and # (nth day-of-week) modifiers. All times are in UTC.
What is the difference between cron and rate expressions?: Cron expressions define specific recurring schedules (e.g., 'cron(0 12 * * ? *)' for noon daily). Rate expressions define simple intervals (e.g., 'rate(5 minutes)' or 'rate(1 hour)'). Use cron for calendar-based schedules and rate for fixed-interval triggers.
Can I schedule in a specific timezone?: EventBridge Scheduler (the newer service) supports timezone-aware scheduling with the ScheduleExpressionTimezone parameter. Classic EventBridge rules always evaluate cron expressions in UTC. If using classic rules, adjust your cron expression to account for the UTC offset.

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