Cron Schedule Calculator

Frequently Asked Questions

Why does my job run more often than expected?

The most common cause is a * in the minute field, which fires every minute. A single misread character turns a daily job into a per-minute firehose. Always verify the minute field first.

How do day-of-month and day-of-week interact?

In Vixie cron, when both fields are restricted, the job fires if either condition is true - an OR. Some implementations use AND semantics. Always test the actual scheduler in your environment.

What timezone are the preview times shown in?

Your browser's local timezone. Your cron server likely runs in UTC or a configured server timezone, which may differ. Adjust accordingly.

Can I schedule the last day of the month?

Standard 5-field cron cannot express the last day of the month. That requires the L extension from Quartz-style syntax. The common workaround is a script that checks whether tomorrow is the 1st.

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How It Works

Cron is the scheduling syntax used by Unix crontabs, CI pipeline schedules, Kubernetes CronJobs, AWS EventBridge, and most serverless schedulers. A standard 5-field expression specifies minute, hour, day-of-month, month, and day-of-week - in that order. A job fires whenever the current time matches all five fields simultaneously.

This calculator parses your expression, validates every field against its legal range, and walks forward minute-by-minute from now to list the next several actual run timestamps in your browser's local timezone. It supports the standard operators (* for every value, a-b for ranges, a,b,c for lists, */n for steps) plus named presets like @daily and @hourly. A one-year search guard catches impossible schedules like February 30 and reports them instead of looping forever.

Use Cases

Cron schedule verification is useful in many DevOps and data engineering contexts:

Confirming that a data pipeline runs at the correct time after switching from UTC to a local timezone offset

Verifying that a maintenance job doesn't overlap with peak traffic hours before deploying it

Debugging a job that appears to fire too often (a bare * in the minute field runs 1440 times per day)

Checking that a month-end reporting job scheduled for the 31st correctly skips February and 30-day months

Documenting the next 10 run times in a runbook to show on-call engineers when to expect scheduled jobs

Tips

The field order is minute, then hour - many people swap them and schedule jobs at the wrong time; always verify the first two fields carefully.

A bare * in the minute field fires every minute of every matching hour - 60 times per hour. Pin the minute to a specific value unless you truly want minute-level frequency.

Named presets like @daily expand to 0 0 * * * - midnight local time. Use them for readability, then verify the expansion in this tool.

Cron servers run in their own timezone, which may differ from your local zone and from UTC. Always specify times relative to the server's timezone and document it explicitly.

Standard cron has minute resolution only. For second-level scheduling, use Quartz-style 6-field expressions or an application-level scheduler.

FAQ

Why does my job run more often than expected?

The most common cause is a * in the minute field, which fires every minute. A single misread character turns a daily job into a per-minute firehose. Always verify the minute field first when a job fires unexpectedly often.

How do day-of-month and day-of-week interact?

In Vixie cron (the most common implementation), when both fields are restricted (not *), the job fires if either condition is true - an OR. This surprises many people. Some implementations use AND semantics. Always test the actual scheduler in your environment with this preview tool.

What timezone are the preview times shown in?

Your browser's local timezone. Your cron server likely runs in UTC or a configured server timezone, which may differ. Adjust the times accordingly before relying on them for scheduling decisions.

Can I schedule the last day of the month?

Standard 5-field cron has no way to express the last day of the month - that requires the L extension from Quartz-style or Kubernetes cron syntax. In plain cron, the closest workaround is running on the 28th or using a script that checks whether tomorrow is the 1st.

Cron Schedule Calculator

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