Tool workspace
Use the common 5-field format: minute hour day-of-month month day-of-week.
Cron Expression Parser
Explain standard five-field cron expressions and validate field ranges without claiming to calculate upcoming execution times. Cron dialects differ, so the target scheduler remains authoritative.
Browser-localFreeNo upload required
What this tool is for
Explain standard five-field cron expressions and validate field ranges without claiming to calculate upcoming execution times. Cron dialects differ, so the target scheduler remains authoritative.
How to use
- Enter a five-field minute/hour/day-of-month/month/day-of-week expression.
- Review the plain-language field summary and any range error.
- Compare the expression with the scheduler's documented dialect, time zone, and day-field semantics.
Example
Parse `0 9 * * 1-5` as minute 0, hour 9, every day of month, every month, and weekday 1 through 5.
FAQ
Will this exactly match my cloud scheduler?
Not necessarily. Compare the target platform's cron dialect and time-zone rules.
Does it calculate the next run?
No. This version validates and explains five fields only.
Reproducible examples
Known inputs and expected results
Run these examples in the workspace above and compare the result with the documented output.
Weekday morning
- Input
- 0 9 * * 1-5
- Options
- Use the documented five-field dialect.
- Action
- Parse all fields.
- Expected output
- Minute 0, hour 9, every day of month, every month, weekdays 1 through 5.
- Explanation
- The parser explains fields; the target scheduler determines its time zone.
Quarter-hour work window
- Input
- */15 8-18 * * 1,3,5
- Options
- Use step, range, and list syntax.
- Action
- Parse and review each field.
- Expected output
- Every 15 minutes during hours 8 through 18 on weekday numbers 1, 3, and 5.
- Explanation
- The expression remains five-field and uses only supported list/range/step forms.
Error or unsupported case
Different scheduler dialect
- Input
- 0 0 9 ? * MON-FRI *
- Expected error or limit
- Seven fields plus ? are not accepted by the five-field parser.
- Safer alternative
- Use the documentation and validator for Quartz or the actual target scheduler.
When not to use this tool
- Calculating guaranteed next-run times
- Quartz, AWS, GitHub Actions, or vendor-dialect equivalence
Algorithm and assumptions
Exactly five fields are validated with documented numeric ranges, wildcards/lists/ranges/steps; day-field semantics and time zones remain scheduler-specific.
Input and output
Input is a five-field cron expression. Output includes validation and a field-by-field explanation, not next-run dates.
Supported formats and behavior
- Wildcards, lists, ranges, and step values
- Standard five-field syntax
- Field-by-field description
Limits
- No seconds or year field
- Quartz, AWS, GitHub Actions, and system cron can differ
Edge cases and common errors
- Day-of-month and day-of-week combination rules vary
- DST can skip or repeat local times
- Macros such as @daily are not accepted unless documented
Release testing
Checks cover known weekday and interval expressions, invalid ranges, unsupported field counts, dialect warning, clear, and mobile controls.
Privacy boundary
The input and result stay in this browser session. ZZP Box does not upload or store the values entered in this tool.
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