Why does my job run at the wrong hour?

Usually a time zone mismatch: cron runs on the server's local time, which may differ from yours or be set to UTC. Check the machine with the date command and convert your schedule accordingly.

What is the difference between * and */5?

* means every value of the field; */5 means every 5th value. So * * * * * runs every minute, while */5 * * * * runs every 5 minutes starting from minute 0.

Why do day-of-month and day-of-week not simply add up?

When both fields are restricted (not *), cron runs the job if EITHER of them matches, not both. That OR semantics surprises most people — restrict only one of the two unless you specifically want it.

Crontab Generator — Guide

Validate and generate crontab and get the human-readable description of the cron schedule.

What it is and when to use it

cron is the time-based scheduler on Unix-like systems, and its expression packs the whole schedule into five fields: minute, hour, day-of-month, month and day-of-week. A single wrong character silently changes when your job runs, so validating the expression and previewing the next run times before committing it to a server saves real debugging time.

Validates a cron expression and translates it into plain language, and can show the coming run times. Verify here before scheduling a job.

How to use it

Enter the cron expression (e.g. */5 * * * *)
Check the human-readable description to confirm the frequency is what you intended
Cross-check against the time preview

A worked example

Fill in a sample expression

*/5 * * * *

Copy this into the tool, or open Crontab Generator

Things that trip people up

The five fields are minute, hour, day-of-month, month, day-of-week — mixing up the order is the most common mistake
Mind the server time zone: cron runs on the machine local time

Questions people ask

Why does my job run at the wrong hour?: Usually a time zone mismatch: cron runs on the server's local time, which may differ from yours or be set to UTC. Check the machine with the date command and convert your schedule accordingly.
What is the difference between * and */5?: * means every value of the field; */5 means every 5th value. So * * * * * runs every minute, while */5 * * * * runs every 5 minutes starting from minute 0.
Why do day-of-month and day-of-week not simply add up?: When both fields are restricted (not *), cron runs the job if EITHER of them matches, not both. That OR semantics surprises most people — restrict only one of the two unless you specifically want it.

Next steps

Open the Crontab Generator tool

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