Cron Expression Generator

A cron expression generator that knows the dialects disagree

Cron is not one language. A Linux crontab, a Quartz trigger, a Kubernetes CronJob, an AWS EventBridge rule and a Jenkins build schedule all borrow the same five characters — * * * * * — and disagree about what they mean. This cron expression generator asks which scheduler you're targeting before it answers, builds a real expression for that dialect, and translates it to the other six with every field it cannot express named explicitly rather than approximated.

The traps this tool is built to catch

• The day-of-month / day-of-week OR rule. In a standard crontab, restricting both fields at once doesn't mean "both must match" — it means "either matches." 30 4 1,15 * 5 runs on the 1st, the 15th, and every Friday, not just a Friday that happens to fall on those dates. The warnings panel names the actual dates.
• Weekday numbering shifts by one. POSIX cron numbers Sunday as 0; Quartz and AWS number Sunday as 1. The same digit means a different day depending on the dialect, and it is silent until the job runs on the wrong morning.
• Field count is ambiguous on its own. A six-field string could be Quartz (seconds first) or AWS (year last) — this tool uses the dialect you picked, and the paste-to-decode path tries every dialect and shows every one that accepts it.
• Quartz's L, W and # have no Unix equivalent. "Last day of the month," "nearest weekday," and "second Tuesday" are real scheduling needs with no standard crontab spelling — converting to Unix reports the gap and, where one exists, a workaround.
• Jenkins' H is not a wildcard. It's a hash of the job's name, deliberately unpredictable, used to spread load so a thousand "every 15 minutes" jobs don't all fire on the same tick. This tool shows the window, not a fabricated exact time.
• DST changes what "every day at 2:30am" means. Some local times don't exist (the clock skips them going forward) and some happen twice (the clock repeats them going back). The next-runs panel marks both rather than picking a plausible-looking instant.

Seven dialects, one schedule

Build the expression once and the portability grid shows it in Linux/Unix crontab, Kubernetes CronJob, Quartz (Java), Spring @Scheduled, AWS EventBridge, Jenkins, and GitHub Actions syntax at the same time — with a note wherever something changed meaning (a weekday renumbered) and a stated reason wherever a dialect simply cannot express the schedule you built.

Common schedules

Forty schedules people actually search for, with the plain-English reading produced by the same engine that reads the box above — click one to load it into the builder.

Field and character reference

The special characters beyond *, ,, - and / are largely a Quartz-family privilege — a plain Unix crontab or a Kubernetes CronJob accepts almost none of them.

Common use cases

• Writing a Kubernetes CronJob schedule and checking it against the cluster's timezone
• Porting a Quartz trigger to a plain crontab, or the reverse, without losing the special characters
• Working out what an inherited crontab line actually does before touching it
• Checking an AWS EventBridge cron(...) expression before it goes into a CloudFormation template
• Confirming a GitHub Actions schedule: won't quietly shift an hour across a DST change
• Settling an argument about whether a step value like */7 actually divides evenly into the hour

Everything happens in this tab

Parsing, translation, linting and the next-run calculation are all computed by JavaScript running in your browser. Nothing you type or paste here — including a crontab line that might contain a real command — is uploaded, logged or stored.