Cron Expression Explainer & Builder
Cron Expression Explainer & Builder works with standard 5-field Unix cron — minute, hour, day-of-month, month, day-of-week — in your browser.
Explanation
At 09:00, on Monday through Friday.
Next runs
Your browser time zone is UTC
Next runs follow the selected time zone. Around a daylight-saving change, a local time that does not exist is skipped and one that occurs twice is listed twice — this is the browser's own behaviour.
Presets
Builder
0 * * * *
Cheatsheet
* — any value, — list (1,15,30)- — range (1-5)/ — step (*/15, 9-17/2)- Field order: minute hour day-of-month month day-of-week
- Example: */10 9-17 * * 1-5
How to use it
- Type a cron expression in the field, or start from a preset
- Read the field-by-field validation and the plain-language explanation
- Check the next runs, and switch between your local time zone and UTC
- Use the builder to assemble an expression from menus, then Apply it and Copy the result
Type an expression to validate it field by field (a broken field gets its own message, such as "Minute must be between 0 and 59"), read a plain-language explanation, and see the next runs. Each field accepts *, a single value, a list like 1,15,30, a range like 1-5, and steps like */15 or 9-17/2; JAN-DEC and SUN-SAT names are resolved, and 0 or 7 both mean Sunday. When day-of-month and day-of-week are both set, a date matches when either one does — the historical Vixie cron rule, which the explanation calls out. A small builder turns menu choices into a valid expression, and seven presets cover the common cases. Next runs are shown for your local time zone or UTC, five or ten at a time; around a daylight-saving change a missing local time is skipped and a repeated one appears twice, following the browser's own behaviour. Unlike the Unix Timestamp Converter, which converts a single instant, this tool describes a recurring schedule. Everything runs locally; your expression is never sent anywhere.
FAQ
Standard 5-field Unix cron: minute, hour, day-of-month, month, day-of-week. Quartz, AWS EventBridge, Jenkins extended syntax and 6- or 7-field variants are not supported. Each field takes *, single values, lists, ranges and steps, plus JAN-DEC and SUN-SAT names.
In order: minute (0-59), hour (0-23), day of the month (1-31), month (1-12, or JAN-DEC), and day of the week (0-7, where 0 and 7 are Sunday, or SUN-SAT). The tool shows the allowed range for each field in its error messages.
This tool follows the historical Vixie cron rule: if only one of the two is restricted, that field decides; if both are restricted, a date matches when either the day of the month or the day of the week matches. The explanation states this whenever it applies.
You choose your browser's local time zone or UTC. In UTC the schedule is fully deterministic. In local time, a daylight-saving change can skip a local time that does not exist or list a repeated one twice — this follows the browser's Date behaviour and is not something the tool resolves.
No. Parsing, the explanation and the next-run calculation all happen in your browser. The expression, your time zone and the computed times are never sent to a server, and analytics records only that the tool was used.