Cron Interpreter — interpret cron schedules online

Each field is an independent constraint. The scheduler walks forward in time and at every minute checks: does the current minute match field 1? Does the hour match field 2? And so on. If all fields match, it fires.

The exception is the day-of-month vs day-of-week pair. Standard cron OR-joins them: 0 0 1 * 1 fires on the 1st of every month OR on every Monday — usually not what you want. Quartz / AWS forbid both being values to avoid this ambiguity, requiring ? in one of them.

• Both day fields restricted — see above. The interpreter flags it.
• Step doesn't wrap — 50-10/20 is invalid; cron does not wrap step ranges across the field boundary.
• Sunday is 0 or 7 — both work in Unix cron; only 1-7 (Sunday=1) in Quartz.
• February 30 — a syntactically valid expression that never fires. The interpreter shows an empty calendar.
• Daylight saving — the spring-forward hour is skipped (no fires there); the fall-back hour is repeated (fires twice). Most schedulers don't alert you.

These are different angles on the same task. The cron reader focuses on the English sentence. The cron decoder focuses on per-field meaning. The cron interpreter on this page focuses on what a scheduler will actually do, including edge cases. All three share the same parser; pick the framing that matches how you think.