A cron expression is a compact way to describe a repeating schedule — "every weekday at 9am", "every 15 minutes", "the 1st of each month". It's used by cron on Linux, CI pipelines, backups and countless schedulers. Here's how to read and write one, with a free parser that explains any expression and shows when it will next run.
Parse a cron expression free →The five fields
A standard cron expression has five fields separated by spaces, in this order:
- Minute (0–59)
- Hour (0–23)
- Day of month (1–31)
- Month (1–12, or JAN–DEC)
- Day of week (0–6, where 0 and 7 are Sunday, or SUN–SAT)
So 0 9 * * 1-5 means minute 0, hour 9, any day, any month, Monday to Friday — i.e. 9:00 on weekdays.
Special characters
Four symbols do most of the work:
- * — every value (every minute, every day, …)
- , — a list, e.g. 1,15 means the 1st and 15th
- - — a range, e.g. 1-5 means Monday through Friday
- / — a step, e.g. */15 means every 15th value
Common examples
- */5 * * * * — every 5 minutes
- 0 * * * * — at the top of every hour
- 0 9 * * 1-5 — 9:00 on weekdays
- 30 2 1 * * — 02:30 on the 1st of every month
- 0 0 * * 0 — midnight every Sunday
The day-of-month / day-of-week quirk
When both the day-of-month and day-of-week fields are restricted (not *), cron runs when either one matches — not both. For example 0 0 1 * 1 fires on the 1st of the month and on every Monday. If only one of the two is set, only that one applies. This trips up a lot of people, so double-check schedules that set both.
Check before you deploy
The safest habit is to preview a schedule before it goes live: read the plain-English description and look at the next few run times. Our free cron parser does exactly that — paste an expression and it shows the schedule and the upcoming runs in your local timezone.
Frequently asked questions
Do all cron systems use five fields?+
The classic Unix format is five fields. Some systems add a seconds field at the front (six fields) or a year at the end; check your scheduler's docs. This guide and our parser use the standard five.
What timezone does cron use?+
Traditionally the server's local time. Many modern schedulers let you set a timezone. Our parser shows the next runs in your device's local timezone.
Is 0 or 7 Sunday?+
Both. In the day-of-week field, 0 and 7 both mean Sunday, so 0 0 * * 0 and 0 0 * * 7 are the same.
The iznkit editorial team builds and documents free, no-sign-up tools for freelancers, small businesses and developers — and writes these guides to go with them.
About iznkit →