Question 1

What does a cron expression look like?

Accepted Answer

A standard cron expression has five fields separated by spaces: minute (0-59), hour (0-23), day of month (1-31), month (1-12), and day of week (0-7, where 0 and 7 are Sunday). Each field can be a number, a list (1,2,3), a range (1-5), a step (*/15), or a wildcard (*).

Question 2

What's the difference between 5-field and 6-field cron?

Accepted Answer

5-field cron starts with the minute field and is the standard format used by Unix cron, GitHub Actions, and Vercel Cron. 6-field cron adds a leading seconds field and is used by Quartz scheduler, Spring, and some other systems. Pick the variant that matches the system you're scheduling on.

Question 3

How do I run a job every X minutes?

Accepted Answer

Use a step value in the minute field: */5 for every 5 minutes, */15 for every 15 minutes. The first run is at minute 0 and then at each subsequent interval.

Question 4

How do I write a cron expression for the last day of the month?

Accepted Answer

Standard cron doesn't have a native 'last day' token. Some implementations (Quartz, AWS) support L for last. With standard cron, the workaround is to run on every day from the 28th and have your script check whether it's actually the last day.

Question 5

Does this work for GitHub Actions and Vercel Cron?

Accepted Answer

Yes. GitHub Actions and Vercel Cron both use standard 5-field POSIX cron. Generate a 5-field expression and paste it into your workflow file or vercel.ts schedule.

Question 6

Can I get an expression for a specific timezone?

Accepted Answer

Cron expressions themselves don't carry timezone information — they're interpreted in the timezone of the system running them. Most schedulers default to UTC. Be explicit about timezone in your scheduler config, then write the expression in that timezone.

Question 7

What does the 'next run times' preview mean?

Accepted Answer

After you generate or paste a cron expression, the tool computes the next five times the job would run if started right now, using your local timezone. Use this to sanity-check that the expression matches what you intended.

Question 8

Why is my cron expression invalid?

Accepted Answer

The most common causes are: a value outside the allowed range (e.g. 60 in the minute field), a missing or extra field, or using day-of-week names in a scheduler that only accepts numbers. The validation panel will point to the offending field.

Cron Expression Generator

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