Free Cron Expression Builder & Parser
Build a cron schedule from simple fields, or paste in an expression to see exactly what it does in plain English.
Fields
* * * * *
Every minute.
Parse an existing expression
The classic cron gotcha: day-of-month and day-of-week are "or," not "and"
Cron's name comes from "chronos," the Greek word for time — the utility has scheduled jobs on Unix systems since the late 1970s, and the same five-field format has stayed essentially unchanged ever since. Its most notorious pitfall lives in the interaction between the day-of-month and day-of-week fields: when both are restricted to something other than *, cron doesn't require a date to match both conditions — it fires if the date matches either one. A schedule like 0 0 13 * 5 ("midnight on the 13th, and midnight every Friday") runs on every Friday and separately on the 13th of every month, not just on a Friday the 13th — the opposite of what most people expect at first glance. This tool's generated description reflects that real behavior directly, spelling out "on the 13th of the month or on Friday" whenever both fields are restricted, specifically so this trap is visible before a schedule ships broken.
Frequently Asked Questions
What order are cron fields in?
Standard 5-field cron reads: minute (0-59), hour (0-23), day of month (1-31), month (1-12), and day of week (0-6, where 0 and 7 both mean Sunday). Some systems add a seconds or year field, but this covers what cron, crontab, and most schedulers expect.
What do the special characters mean?
* means "every value." A comma list like 1,15 means those specific values. A range like 1-5 means every value in between. A step like */15 means every 15th value starting from the field's minimum, and 0-30/10 combines a range with a step.
What happens if I set both day-of-month and day-of-week to specific values?
Cron treats them as "or," not "and" — the job runs whenever either condition matches, not only when both do. Setting day-of-month to 13 and day-of-week to Friday runs the job on every Friday plus separately on the 13th of every month, not just on a Friday the 13th, which is a common source of confusion.
Where does the name "cron" come from?
From "chronos," the Greek word for time. The utility has been part of Unix-based systems since the late 1970s, and the same five-field scheduling format is still the standard today.
How do I schedule something for weekdays only?
Set the day-of-week field to 1-5 (Monday through Friday) and leave day-of-month as *. For example, 0 9 * * 1-5 runs at 9:00 AM every weekday.
Can I paste in an existing cron expression?
Yes — paste any 5-field cron expression into the parser box and it fills in the individual fields and generates a plain-English description, so you can check what a schedule you found online or inherited from a teammate actually does.