Fake Data Generator
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Cron Expression Generator
Build a cron schedule from controls and see the next times it runs.
Each field accepts a value, a list such as 1,15, a range such as 1-5, a step such as */15, or any combination.
Quick Tool Overview
The Cron Expression Generator builds a schedule from controls, describes it back in plain English, and shows the next times it will actually fire — which is what catches a mistake before it costs a week.
- What it does
- Builds and verifies a cron expression
- You give it
- A frequency, or values per field
- You get back
- The expression, a description and the next run times
- Best for
- Writing a crontab, a CI schedule or a CronJob
About the Cron Expression Generator
Choose when a job should run and the expression is built for you, described back in plain English, and checked by showing the next several times it will actually fire. That last part is what catches a mistake before it costs you a week.
Every field supports the full syntax — lists, ranges, steps and names — and each control explains what it produces. The trap the generator warns about is the one nobody expects: when both day of month and day of week are restricted, cron treats them as OR rather than AND, so "the 1st and also Mondays" runs far more often than intended. The shorthand forms such as @daily and @reboot are available too, with what each expands to.
Key features of the Cron Expression Generator
Next runs calculated
Stepped forward minute by minute and tested, exactly as cron does — not estimated from the fields.
The OR trap warned about
Restricting both day of month and day of week means either, not both. It is the single commonest cron mistake and it is flagged.
Full field syntax
Lists, ranges, steps and month and day names, each explained where you use it.
Shorthands included
@daily, @weekly, @reboot and the rest, with what each expands to rather than just the name.
Plain-English readback
The description is the fastest way to notice that an expression does not say what you meant.
How to use the Cron Expression Generator
-
1
Pick a frequency
Every minute, hourly, daily, weekly, monthly, or a custom pattern.
-
2
Set the fields
Minute, hour, day, month and weekday, each with lists, ranges and steps.
-
3
Read it back
The plain-English description is the quickest way to catch a mistake.
-
4
Check the next runs
The next several fire times, calculated rather than assumed.
Frequently asked questions
Minute, hour, day of month, month, day of week — in that order. An asterisk means every value, and the first field being minutes is why 0 0 * * * is midnight rather than every hour.
Almost certainly because you restricted both day of month and day of week. Cron ORs those two fields, so "1st of the month" and "every Monday" together means both, not their intersection.
The server's local time zone, which is often UTC and often not what you assumed. Daylight saving makes an early-morning job run twice or not at all on the changeover days.
It runs the job once when the machine starts and never again on a schedule. Useful for starting a service, and a common surprise when someone expects it to mean something periodic.
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