Cron Expression Parser & Next Run Times
ConversionEverything runs locally in your browser — nothing is uploaded
Turn something like “*/15 9-17 * * 1-5” into plain English: each field is explained in turn, a one-line summary follows, and the next few run times are listed. Times are found by jumping to the next possible match rather than testing every minute, so even a schedule pinned to 29 February resolves instantly. An expression that can never fire — 31 February, say — is reported with the reason instead of leaving the page spinning.
Features
- All the usual syntax: star, single value, a-b ranges, a,b,c lists and /n steps on stars or ranges
- Month and weekday names (JAN-DEC, SUN-SAT) are accepted
- Per-field explanation plus a one-line summary such as "every 15 minutes of 09:00 to 17:00 on Monday to Friday"
- Lists the next 1-50 run times with the weekday for each
- Applies the classic day-of-month / day-of-week OR rule (Vixie cron semantics)
- Understands the @daily, @hourly, @weekly, @monthly and @yearly macros
- Impossible schedules are rejected up front, naming the fields that cannot line up
- Run times can be shown in local time or UTC, since server crons usually run in UTC
How to use
- Paste a 5-field cron expression into the box
- Choose the description language, how many runs to list, and the timezone
- Click Run (or press Ctrl/⌘ + Enter)
- Copy the result, or fix the expression using the breakdown
FAQ
- Why was my 6-field expression rejected?
- A leading seconds field is the Quartz and Spring convention; classic cron has five fields. Reading a 6-field expression as 5 fields shifts every field by one, so the run times you get back are for a completely different schedule — this tool refuses it and asks you to drop the seconds field rather than guess.
- What happens when both day-of-month and day-of-week are set?
- Classic (Vixie) cron treats them as an OR: “0 0 1 * 1” fires on the 1st of the month, or on any Monday. Only when one of the two is a star does it become an AND. Many implementations get this wrong; this tool follows Vixie.
- Which timezone are the run times in?
- Either, and it defaults to local time. Containers and servers usually run cron in UTC while local time is easier to sanity-check by hand, so both are offered. Switching shifts every listed time — and the weekday shown along with it.
- Why does it say the expression can never fire?
- For example “0 0 31 2 *”: February has no 31st in any year, so it never runs. The tool checks whether the day and month combinations exist at all. On top of that there is a four-year search limit (leap-year gaps can reach eight years); past the limit it reports that nothing was found instead of searching forever.
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