How to Build a Cron Expression
Choose a preset or edit the five cron fields, then review the expression and plain-English description. Copy it into a scheduler only after checking that scheduler’s syntax and timezone. This page generates text and does not create a running job.
The Five Cron Fields Explained
The fields represent minute, hour, day of month, month and day of week. Asterisks, ranges, lists and steps describe allowed values. Day-of-month and day-of-week interactions differ across implementations.
Common Cron Schedule Examples
*/5 * * * * describes every five minutes in a typical five-field cron implementation. 0 0 * * * commonly means midnight daily. The scheduler’s timezone determines when midnight occurs.
Cron Expression to Plain English
The human-readable description helps catch an accidental field position or step. It is an explanation of supported syntax, not a simulation of every scheduler behavior. Validate edge cases such as daylight-saving changes in the actual system.
Cron Differences Across Platforms
Some schedulers add seconds or years, use different weekday numbering, or support special tokens. Cloud platforms may also impose timezone conventions. Consult the target scheduler before assuming a five-field expression is portable.
More examples and technical details
What Cron Is
Cron is the job scheduler that has shipped with Unix systems for decades. You hand it an expression that describes when something should run, and it runs that thing on exactly that schedule, forever, without you thinking about it again. A cron expression is five fields separated by spaces, and each field controls one part of the timing.
| Field | Range | What it means |
|---|---|---|
| Minute | 0 to 59 | The minute of the hour the job fires. |
| Hour | 0 to 23 | 24-hour clock, so 0 is midnight and 13 is 1pm. |
| Day of month | 1 to 31 | Calendar date within the month. |
| Month | 1 to 12 | 1 is January, 12 is December. |
| Day of week | 0 to 6 | Sunday is 0 (and on many systems 7 too). |
The Special Characters
Four symbols do most of the work inside those five fields. An asterisk means every value, so an asterisk in the hour field means every hour. A comma builds a list, so 1,15,30 in the minute field fires at three specific minutes. A hyphen makes a range, so 1-5 in the day-of-week field covers Monday to Friday. A slash sets a step, so */15 in the minute field means every fifteenth minute starting from zero.
Common expressions
| Expression | Runs |
|---|---|
| 0 * * * * | Every hour, on the hour. |
| 0 0 * * * | Every day at midnight. |
| 0 9 * * 1-5 | 9am on weekdays, Monday through Friday. |
| */5 * * * * | Every 5 minutes. |
| 0 0 1 * * | Midnight on the 1st of every month. |
The Day-of-Month vs Day-of-Week Gotcha
Here is the trap that surprises almost everyone. When you set both the day-of-month field and the day-of-week field to real values, most cron implementations run the job when either one matches, not when both do. So "0 0 13 * 5" does not mean the 13th only if it is a Friday; it means every 13th and every Friday. If you actually need both conditions to line up, you generally have to check the date inside the script itself.
Cron syntax reaches well past the original Unix crontab now. You will find the same five fields in CI pipeline schedules, GitHub Actions workflows, Kubernetes CronJobs, and the managed schedulers in every major cloud. Learn it once and the knowledge travels everywhere.
The generator above builds and explains expressions right in your browser, translating each field into plain English as you go so you can trust what you are about to schedule.
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Frequently asked questions
What does a cron expression mean?
It specifies which calendar field values trigger a scheduled job in a cron-compatible scheduler.
How do I run a job every 5 minutes?
In standard five-field cron, use */5 * * * *.
How do I schedule a cron job daily?
For midnight daily, use 0 0 * * * and check the scheduler’s timezone.
Do all cron implementations use the same fields?
No. Some include seconds, years or special tokens and have different day-field rules.
Does the generator run any jobs?
No. It generates and explains expressions only.