Cron Explainer

How to read a cron expression

A cron expression is five fields, left to right: minute (0–59), hour (0–23), day of month (1–31), month (1–12), day of week (0–7, where both 0 and 7 mean Sunday).

1. Type the expression into the box above. The explanation appears as you type.
2. Read the sentence — it says exactly when the job runs, with no cron knowledge needed.
3. Check the breakdown to see what each individual field contributed.

The special characters

* means "every" (every minute, every hour…). A comma lists values: 1,15 means "on the 1st and 15th". A dash is a range: 1-5 means "1 through 5". A slash is a step: */15 means "every 15", and 9-17/2 means "every 2, from 9 to 17". Month and day-of-week fields also accept names: JAN–DEC and MON–SUN.

Common patterns, decoded

What is a cron expression?

A cron expression is a five-field string (minute, hour, day of month, month, day of week) that schedules recurring jobs on Unix-like systems. For example, 0 9 * * 1-5 runs at 9:00 AM, Monday through Friday.

What does */15 mean in cron?

The slash sets a step: */15 in the minute field means every 15 minutes (at minutes 0, 15, 30, and 45). A range with a step, like 9-17/2 in the hour field, means every 2 hours from 9 AM to 5 PM.

Can I use names like MON or JAN?

Yes. The month field accepts JAN through DEC and the day-of-week field accepts SUN through SAT, in any letter case. Full names like Monday work in this explainer too.

What happens when both day of month and day of week are set?

Standard cron runs the job when either field matches, not both. This explainer says 'or' in that case so the meaning stays clear.

Is 0 or 7 Sunday in the day-of-week field?

Both. This explainer accepts 0 and 7 for Sunday, matching standard cron behavior.

Does this cover seconds or years?

No. This is the classic five-field cron format used by Unix cron and most schedulers. Some systems add a seconds field at the start or a year at the end — those six- and seven-field variants are not covered here.