Cron Expression Builder

0 9 * * 1-5

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Five fields, one job

Cron syntax is famously dense — five fields, each accepting wildcards, ranges, lists, and steps. Writing one from scratch every time invites typos and off-by-one errors. This builder lets you construct a cron expression visually using dropdowns and presets, see the resulting string, read a plain-English summary, and verify against the next five real fire times in your local timezone before deployment.

Servers, Kubernetes, and cloud schedulers

• Setting up a new crontab entry on a Unix/Linux server or scheduling task on any platform that accepts standard 5-field cron syntax.
• Configuring a Kubernetes CronJob, GitHub Actions workflow schedule, AWS EventBridge rule, or any cloud scheduler that uses cron expressions.
• Translating a business requirement — "run every weekday at 09:00", "backup on the 1st and 15th", "execute every 30 minutes except weekends" — into a syntactically correct, tested expression.
• Debugging a cron job that doesn't fire when expected; use the preview to confirm the expression matches your intent.
• Onboarding developers unfamiliar with cron syntax; the dropdowns and real-time preview teach the syntax faster than documentation.

Building a schedule visually

• Start with a preset or blank fields. Choose from common schedules (every 5 minutes, weekdays 9 AM, monthly, etc.) or build from five empty fields: minute, hour, day, month, weekday.
• Edit fields individually or type syntax. Use dropdowns for simple selections, or paste/type cron syntax directly: */5, 9-17, 1,15, 0-30/5, and so on.
• Watch the preview update in real time. The tool generates the five-field cron string, shows a human-readable interpretation, and lists the next five fire times in your browser's local timezone.
• Copy the expression and deploy. Once you're satisfied, copy the cron string and paste it into your server, job scheduler, or cloud platform. Always confirm the timezone assumption with your target system.

Wildcards, ranges, lists, and steps

• * — every value in the field's range.
• */N — every Nth interval, starting at the lower bound (e.g. */15 in minutes = 0, 15, 30, 45).
• A-B — range, inclusive (e.g. 9-17 in hours = 9 AM to 5 PM).
• A,B,C — comma-separated list of specific values (e.g. 1,15 in day = 1st and 15th).
• A-B/N — every Nth within range A–B (e.g. 0-30/5 = 0, 5, 10, 15, 20, 25, 30).

OR logic, timezones, and Quartz traps

• Day-of-month and day-of-week interact via OR. If you specify both a day-of-month and a day-of-week (neither *), cron fires when either matches. * * 15 * 1 runs on the 15th OR any Monday, not "only on the 15th if it's a Monday".
• Timezone mismatch. This tool shows fire times in your browser's local timezone for convenience. Real cron daemons run in the server's timezone (often UTC). Always verify the target system's timezone before deploying.
• */N isn't "every N from the current time". */15 in minutes always produces 0, 15, 30, 45 — not a rolling 15-minute interval. Use a list if you need a specific phase.
• Non-standard cron flavours use extra fields. Quartz scheduler uses 6–7 fields (adding seconds and optionally year). systemd timers use a completely different format. This tool targets the standard 5-field crontab syntax.
• Complex logic is awkward in cron. Conditions like "Friday the 13th only" or "every third Tuesday" can't be expressed cleanly; you'll need a wrapper script to filter.

Assembling a weekday-morning schedule

Set minute 0, hour 9, day-of-month *, month *, day-of-week 1-5. The builder assembles 0 9 * * 1-5, explains it as "At minute 0, hour 9, on Mon–Fri.", and lists the next five real fire times in your local timezone so you can eyeball them before shipping. Change day-of-week to */2 in the minute field and it re-validates instantly, rejecting anything out of range with the field's valid bounds.

Day-of-month vs day-of-week, phase offsets, and extra fields

Does * * 15 * 1 run only on the 15th if it's a Monday? No — it fires on the 15th OR on any Monday. When both day-of-month and day-of-week are restricted, standard cron ORs them together. Matching "the 15th only when it's a Monday" needs a wrapper script that checks the date.

The preview times don't match when my job actually runs. The preview uses your browser's timezone; real cron daemons run in the server's timezone, usually UTC. Convert your intended local time to the server's zone before deploying.

Is */15 "every 15 minutes from now"? No. It's a fixed phase from the start of the range — minutes 0, 15, 30, 45 — not a rolling interval anchored to the current time. Use an explicit list like 7,22,37,52 if you need a different phase.

My 6- or 7-field expression won't parse. This builder targets the standard 5-field crontab. Quartz (used by Java schedulers) adds seconds and an optional year, and systemd timers use an entirely different syntax — neither is 5-field cron.