AWS EventBridge Cron Checker

AWS EventBridge Cron Format

AWS EventBridge (formerly CloudWatch Events) uses a 6-field cron format that differs from standard Unix cron. The format is:

minute hour day-of-month month day-of-week year

The most important difference from standard cron is the mandatory ? wildcard: you must use ? in exactly one of the day-of-month or day-of-week fields. You cannot use * in both — one must be ? to indicate “no specific value.”

Field Reference

• Minute (0–59)
• Hour (0–23)
• Day-of-month (1–31) — Supports L (last day) and W (nearest weekday)
• Month (1–12 or JAN–DEC)
• Day-of-week (1–7 or SUN–SAT, where 1 = Sunday) — Supports L (last occurrence) and # (nth occurrence)
• Year (1970–2199 or *)

Special Characters

• * — All values
• ? — No specific value (required in exactly one of day-of-month or day-of-week)
• - — Range: MON-FRI
• , — List: 1,15,28
• / — Step: */5 = every 5 units
• L — Last: last day of month (L in day-of-month) or last Saturday (7L in day-of-week)
• W — Nearest weekday: 15W = nearest weekday to the 15th
• # — Nth occurrence: 2#1 = first Monday (day 2 = Monday, #1 = first)

Example Expressions

• 0 9 * * ? * — Every day at 9:00 AM UTC
• 0 18 ? * MON-FRI * — Weekdays at 6:00 PM UTC
• 0 12 1 * ? * — First of every month at noon UTC
• */5 * * * ? * — Every 5 minutes
• 0 8 ? * 2#1 * — First Monday of every month at 8:00 AM UTC
• 0 0 L * ? * — Last day of every month at midnight UTC
• 30 6 ? * MON * — Every Monday at 6:30 AM UTC

EventBridge vs Standard Cron

Standard Unix cron uses 5 fields (minute, hour, day, month, weekday) where day-of-week is 0–7 (0 and 7 = Sunday). EventBridge cron uses 6 fields (adds year), day-of-week is 1–7 (1 = Sunday), and requires the ? wildcard in either the day-of-month or day-of-week field. If you need to validate standard 5-field cron expressions, use our Cron Job Checker instead.