Does this support 6-field cron (with seconds)?

No. This is a 5-field tester (minute / hour / day-of-month / month / day-of-week), which is what Linux cron, Kubernetes CronJobs, GitHub Actions, and most cloud schedulers accept. Quartz-style 6-field cron (with seconds) is used by Spring, AWS EventBridge, and a few others; for those, treat the first field as seconds and the rest as the 5-field version.

Why does my cron expression run twice on the day a month starts on a specific weekday?

When both day-of-month and day-of-week are specified (neither is *), most cron implementations treat them as an OR, not an AND. So '0 0 1 * 1' fires on the 1st of every month AND every Monday, which is rarely what authors want. To get the intersection ('first Monday of the month'), use a scheduler that supports day-of-week constraints like 1#1 or restructure your job logic.

Cron Expression Tester

MonitoringMulti-Cloud

Parse 5-field unix cron expressions, see human-readable descriptions, and preview next execution times.

Last verified: May 2026

Cron Expression

Minute

0-59

Hour

0-23

Day of Month

1-31

Month

1-12 or JAN-DEC

MON-FRI

Day of Week

0-6 or SUN-SAT

Raw Output

Output will appear here...

See It in Action

A nightly database backup CronJob is silently missing runs once a week. You paste its schedule (0 2 * * 1-5) into the tester. The next-runs list shows 2am Mon–Fri — exactly what was intended. But your production timezone is UTC and the cluster runs in America/Chicago, so '2am' is actually 7am UTC, and the database snapshot window expires at 6am UTC. Move the job earlier, add a TZ annotation, run the tester again to confirm.

What This Tool Does

Cron expressions look simple until they don't. Is */5 in the day-of-month field every five days, or every fifth listed day? Does 0 0 * * 0 mean midnight every Sunday or midnight every weekday? The Cron Expression Tester parses a standard 5-field Unix cron expression, translates it into a plain-English description, and lists the next ten execution times in your local timezone so you can confirm intent before deploying it to a scheduler.

Technical Details

The parser tokenizes each of the five fields, expanding ranges (1-5), step values (*/15), and lists (1,15,30) into a set of allowed values. The next-runs calculation walks forward from the current time in one-minute increments, checking each minute against the allowed sets for all five fields, and collects the first ten matches. Day-of-month and day-of-week are combined with the OR semantics described above to match standard Unix cron behavior.

Common Use Cases

1Verifying that a Kubernetes CronJob, GitHub Actions schedule, or AWS EventBridge rule fires when you intend before it goes to production.
2Sanity-checking a cron line in a Linux crontab or a systemd OnCalendar expression that you have not touched in months.
3Translating a business requirement ('run every weekday at 6:30am, but not on the first of the month') into a cron expression by iterating until the next-runs list matches expectations.
4Debugging a job that ran at an unexpected time by pasting the schedule and reading the next-runs window to see what cron actually thinks the schedule means.

Common Questions

Does this support 6-field cron (with seconds)?: No. This is a 5-field tester (minute / hour / day-of-month / month / day-of-week), which is what Linux cron, Kubernetes CronJobs, GitHub Actions, and most cloud schedulers accept. Quartz-style 6-field cron (with seconds) is used by Spring, AWS EventBridge, and a few others; for those, treat the first field as seconds and the rest as the 5-field version.
Why does my cron expression run twice on the day a month starts on a specific weekday?: When both day-of-month and day-of-week are specified (neither is *), most cron implementations treat them as an OR, not an AND. So '0 0 1 * 1' fires on the 1st of every month AND every Monday, which is rarely what authors want. To get the intersection ('first Monday of the month'), use a scheduler that supports day-of-week constraints like 1#1 or restructure your job logic.

Expert Tips

TIP

Avoid scheduling everything on the minute boundary (0 * * * *) — every cluster in the world hits that boundary, and shared resources (AWS API endpoints, package mirrors) get spiky load there. Pick a random minute offset for non-coordinated jobs.

TIP

If a job must not overlap with itself, do not rely on cron to enforce that. Cron will happily start a second copy if the first is still running. Use a wrapper like flock, a Kubernetes Job's concurrencyPolicy: Forbid, or an in-script PID/lock file.

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