Cron expression parser and next run calculator
About Cron Expression Parser
The cron expression parser checks a standard five-field Unix schedule, explains it in plain English and lists the next run times. Paste a crontab expression such as */15 9-17 * * 1-5 to check a deploy job, backup, report or maintenance task before it goes live.
Runs in your browser. Nothing is uploaded, so private infrastructure schedules stay on your machine. Choose local time or UTC and preview the next 5, 10 or 20 runs.
The parser targets portable five-field Unix cron: minute, hour, day of month, month and day of week. It supports wildcards, comma lists, ranges, steps, month names and weekday names. It rejects vendor extensions such as seconds, years, L, W, # and Quartz question marks, because reading them as Unix cron would be ambiguous.
How it works
Read the five cron fields
A Unix 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) and day of week (0-7, where 0 and 7 both mean Sunday). The parser checks the field count and the range of every value.
Use lists, ranges and step values
An asterisk matches every value. A comma makes a list, a hyphen makes an inclusive range and a slash sets a step. For example, */10 means every ten units, 9-17 limits hours to the working day, and MON-FRI limits days to Monday through Friday.
Understand day-of-month and weekday matching
Traditional Unix cron has a special rule. When both day of month and day of week are restricted, the job runs on a date that matches either field. When one of them is an asterisk, the other one decides. The summary points this out for schedules where it matters.
Preview runs in local time or UTC
Local evaluates the schedule in your browser's time zone. UTC removes local offsets. Each result shows a readable date, an ISO 8601 timestamp and Unix seconds. Daylight saving changes follow the calendar rules of the selected time zone.
Frequently asked questions
What cron syntax does this parser support?
Standard five-field Unix cron with numbers, *, comma lists, inclusive ranges, positive steps, and three-letter English month and weekday names. It does not accept a seconds or year field.
Why does my Quartz or AWS cron expression fail?
Quartz, AWS EventBridge and some other schedulers use six or seven fields and add tokens such as ?, L, W or #. Those are different dialects. This tool rejects them, because reading a vendor extension as Unix cron could give you the wrong schedule.
Are Sunday values 0 and 7 both accepted?
Yes. In the day-of-week field, 0 and 7 both mean Sunday. You can also write SUN. Other weekdays use 1 through 6 or MON through SAT.
Which time zone is used for the next run calculation?
You pick local time or UTC. Local uses the time zone set on your device. UTC evaluates all five fields in UTC. The result states which zone was used.
Is the cron expression sent to a server?
No. Parsing, validation, the explanation and the next-run list all run in your browser.
Sources & last verified
We checked this tool's behavior and the claims on this page against the specifications below on . The tool runs in your browser, so the output you see is exactly what the engine produced.
Found a wrong result or an outdated claim? Report an error and we will check it again.
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