Cron Parser
Preview five-field numeric Cron with timezone and date anchor
Five numeric Cron fields: *, lists, ranges, */n and a-b/n. Restricted day-of-month and weekday use OR; a day field starting with * uses AND.
βββββThe full guide also includes pitfalls, worked examples, snippets, FAQs, and related tools for checking results or troubleshooting.
About this tool
Preview a bounded five-field numeric Cron subset: minute 0β59, hour 0β23, day-of-month 1β31, month 1β12 and weekday 0β7, with both 0 and 7 meaning Sunday. Supported forms are *, decimal integers, a-b ranges, comma lists, */n and a-b/n; steps start at the range minimum. Names, seconds, macros, single-value steps such as 5/10, Quartz operators and wraparound ranges are rejected. When both day fields are restricted, day-of-month OR weekday can match. If either day field starts with *, both day tests must match. Choose a browser-supported timezone and optionally an ISO instant with Z or Β±HH:mm as the starting point. The preview returns up to five instants strictly after that anchor and within 365 elapsed days; a valid schedule can have no match in that horizon. Missing clock times are skipped and repeated times are listed twice with distinct ISO instants. Real schedulers can differ in DST, missed-job and dialect policies. Expressions and settings are stored locally; Clear removes the draft.
Failure Clinic (Common Pitfalls)
No match is not full schedule validation
Cause: The preview horizon is bounded and a runtime can use a different Cron dialect.
Fix: Validate the expression in the actual scheduler and test its DST and missed-run policies.
An interval step restarts within its field
Cause: */10 in minutes means 0,10,20,30,40,50 each hour; it is not ten minutes after an arbitrary prior execution.
Fix: Use interval scheduling when elapsed duration from the previous run is required.
Scenario Recipes
Verify day-of-month OR weekday
Goal: Catch a schedule that is broader than first-Monday-only.
- Enter 0 9 1 * 1, timezone UTC, anchor 2026-03-01T00:00:00Z.
- Analyze and inspect March 1, March 2 and later Mondays.
Result: March 1 at 09:00 and March 2 at 09:00 both match. This expression is not limited to the first Monday.
Preview a repeated 01:30
Goal: See the preview policy across a New York rollback.
- Enter 30 1 * * *, timezone America/New_York, anchor 2026-11-01T04:00:00Z.
- Analyze and compare the first two ISO instants.
Result: The first two are 2026-11-01T05:30:00.000Z and 2026-11-01T06:30:00.000Z.
Production Snippets
Worked example
text
0 9 1 * 1 β first of month OR Monday at 09:00
0 0 31 2 * β no matching calendar date
30 1 * * * β rollback can produce two local 01:30 instantsFrequently Asked Questions
Which Cron syntax is supported?
Five numeric fields using *, decimal values, ranges, lists, */n and a-b/n. Sunday is 0 or 7. Names, seconds, @daily-style macros, 5/10, ?, L, W, # and wraparound ranges are not supported.
Are day-of-month and weekday combined with AND or OR?
If neither day field starts with *, they use OR. In 0 9 1 * 1, 09:00 on every Monday and on every first of the month match. If either day field starts with *, both day tests must match.
Why are fewer than five runs shown?
Only matches within 365 elapsed days after the anchor are searched. Annual or leap-day schedules may yield fewer than five or none; no match does not by itself mean invalid syntax.
What happens during DST changes?
The preview skips nonexistent local minutes and lists both instances of repeated minutes, each with a different ISO instant. Your scheduler may apply another policy; compare its own next-run output.
Does changing the summary rerun the search?
No. Input changes clear stale output; Analyze runs the search. The summary toggle only changes presentation. Expressions, anchor and settings are stored locally and Clear removes them.
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