Which part of a cron expression is most commonly mixed up?

Double-check the day-of-week field specifically before deploying a schedule — it's the field most commonly mixed up, since some systems count Sunday as 0 and others as 7.

Which cron formats does it accept?

Standard five-field expressions, shortcut words that start with an at sign such as @daily, and expressions of six or seven fields, which trigger a warning because seconds or year fields follow platform-specific rules. Anything else is rejected with a message.

Why am I told that day of month and day of week are both set?

In standard cron, when both fields hold something other than a star or question mark, a job runs when either matches. People often expect both to match. The amber note appears so you can double-check the intent.

Which time zones can I choose?

Your browser's detected zone and UTC, nothing else. If your browser already reports UTC, only that one option is offered. The run times use your device clock as the starting point.

What does This schedule never runs mean?

The expression is valid, but no real date can match it, such as the 31st of February. The tool finds no upcoming run times and shows that note, so you can fix the day or month field.

Is Sunday 0 or 7 in the Day of week field?

The field hint reads 0-7 or SUN-SAT, so this tool accepts both 0 and 7 for Sunday, and names such as MON-FRI. Other systems may number days differently, so check the documentation of your scheduler.

Home/Security & Developer/Cron Expression Builder

Cron Expression Builder

Build and understand cron expressions in plain English

Files never storedRuns on your device

Cron Expression

Minute (0-59)

Hour (0-23)

Day of month (1-31)

Month (1-12 or JAN-DEC)

Day of week (0-7 or SUN-SAT)

In plain English

At 09:00, Monday through Friday

Next 5 runs in

Thu, Nov 5, 2026, 09:00:00
Fri, Nov 6, 2026, 09:00:00
Mon, Nov 9, 2026, 09:00:00
Tue, Nov 10, 2026, 09:00:00
Wed, Nov 11, 2026, 09:00:00

The schedule is read as clock time in the selected zone, so 09:00 means 09:00 there. Servers, GitHub Actions and Kubernetes CronJobs usually run cron in UTC, so pick UTC to see their runs; the times shown are not converted between zones.

Common presets

Reading results never uses a trial use. Copying, saving or printing uses 1 per visit.

About Cron Expression Builder

Builds and explains cron expressions — the schedule syntax used to automate recurring tasks on a server — translating between the cryptic expression and a plain-English description.

Watch: Cron Expression Builder in Action

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How to use Cron Expression Builder

Type a schedule into the Cron Expression box, or edit the five boxes underneath labelled Minute, Hour, Day of month, Month and Day of week. Each box has a dropdown of common values such as */15 or 9-17. The starting expression is 0 9 * * 1-5.

A valid expression shows an In plain English sentence, written with a 24-hour clock, and a list of the next five run times. The Time zone selector above that list switches between your browser's zone and UTC. Below, six Common presets fill the box when clicked: Every minute, Every hour, Every day at midnight, Every Monday at 9am, First day of every month and Every 15 minutes. Invalid input shows a red Invalid cron expression card with the reason, and amber notes appear when something looks risky.

When to use it

Reach for it when you inherit a crontab line and need to confirm what it really does, or when you are about to deploy a schedule and want to see concrete upcoming run times before it goes live. It also helps when you are turning a plain request such as weekdays at nine into the five fields, or comparing the same schedule in your local zone and in UTC.

When not to use it

Do not treat it as the final word for platforms with their own dialect. Quartz, AWS EventBridge and some CI services use different field counts and special characters, and this tool can only warn when it sees six or seven fields. For those, confirm in the platform's own console. It also cannot tell you how a given server handles daylight-saving shifts or runs missed while it was off.

Tips for best results

When Day of month and Day of week are both set to something other than a star, standard cron runs on days matching either one, not both, and the tool shows an amber warning to remind you. Try 0 0 1 * 1 to see it: the run list mixes first-of-month dates with Mondays. Compare the UTC and local lists before deploying to a server whose clock is set to UTC.

Limitations

The English sentence comes from one description library and the run times from a separate scheduling library, so on unusual expressions they can disagree slightly with your real scheduler. Only five run times are listed, and the time zone choice is limited to your browser's zone and UTC. The five field boxes stay blank unless the expression has exactly five fields, so edit six-field expressions in the main box.

Privacy

Parsing, the English description and the next-run calculation are done by libraries bundled with the site and run in your browser, using your device clock and time zone. The expression you type is not transmitted anywhere. A usage record with the tool name and a device identifier may be sent, but it does not contain the schedule.