Cron expression translator: plain English and next run times

Questions

FAQ

Which cron syntax does this support?

Standard 5-field POSIX cron: minute, hour, day-of-month, month, day-of-week. Each field accepts the usual operators — comma lists, hyphen ranges, asterisk wildcards, and slash steps (e.g. */5 or 0-30/10). It does not yet support extended Quartz syntax (seconds field, year field, L/W/# operators).

Why are day-of-month and day-of-week treated specially?

Standard cron has a quirk: when both day-of-month and day-of-week are restricted, the schedule fires on either match, not both. So "0 0 1 * 1" fires on the 1st of every month AND on every Monday — not just Mondays that fall on the 1st. We follow this convention because virtually every cron implementation does.

Does the next-fire-time preview honour DST?

Yes. Each candidate time is resolved in the time zone you select with the IANA rules. The preview skips local times that do not exist (02:30 on the night clocks spring forward) and lists times in the repeated autumn hour twice (01:30 on the night clocks fall back). Real schedulers handle these nights differently: cronie, for example, runs jobs from a skipped hour right after the change and does not run fixed-time jobs twice. Check your scheduler's documentation.

Why doesn't the description match what I expected?

Plain-English description of cron is a translation, and translations have edge cases. If you see "every minute of every hour" instead of "every minute," it's because both fields use the wildcard. The description is best-effort — the next-fire-times list is the authoritative source of truth for what your job will actually do.