Realm by Rook|Utilities
    Cron Expression Builder

    Cron Expression Builder

    Build, test, and explain cron schedules with next-run preview

    Minute
    */15
    Hour
    *
    Day of month
    *
    Month
    *
    Day of week
    *
    In plain English
    at minutes 0, 15, 30, 45 of hours 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23
    Next 10 executions (local time)
    1.Sat, Apr 25, 2026, 08:45 AM(4 min from now)
    2.Sat, Apr 25, 2026, 09:00 AM(19 min from now)
    3.Sat, Apr 25, 2026, 09:15 AM(34 min from now)
    4.Sat, Apr 25, 2026, 09:30 AM(49 min from now)
    5.Sat, Apr 25, 2026, 09:45 AM(64 min from now)
    6.Sat, Apr 25, 2026, 10:00 AM(79 min from now)
    7.Sat, Apr 25, 2026, 10:15 AM(94 min from now)
    8.Sat, Apr 25, 2026, 10:30 AM(109 min from now)
    9.Sat, Apr 25, 2026, 10:45 AM(124 min from now)
    10.Sat, Apr 25, 2026, 11:00 AM(139 min from now)
    Common patterns
    Cron syntax reference
    * any value
    , value list (e.g. 1,3,5)
    - inclusive range (e.g. 1-5)
    / step (e.g. */15 = every 15)
    @yearly @monthly @weekly @daily @hourly shortcuts
    Month names: Jan, Feb, …, Dec
    Day names: Sun, Mon, …, Sat (Sunday = 0 or 7)

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    About the Cron Expression Builder

    A cron expression is a 5-field schedule descriptor used by Unix cron, Kubernetes CronJobs, GitHub Actions, Vercel, AWS EventBridge, and nearly every scheduler. The syntax is compact but easy to get wrong — this builder validates it, describes it in English, and shows you the next 10 times it will fire so you can sanity-check before deploying.

    Features

    How it works

    1. Type or click a preset to load a cron expression.
    2. Read the per-field breakdown and the plain-English description.
    3. Review the next 10 execution times to confirm the schedule matches your intent.
    4. Copy the expression into your crontab, CI config, or scheduler.

    Use cases

    Frequently asked questions

    What cron dialect does this use?

    +

    Standard 5-field POSIX cron (minute hour day-of-month month day-of-week). No seconds field, no Jenkins-style H, no AWS Lambda's 6-field dialect.

    How does it handle the day-of-month + day-of-week combo?

    +

    Per the POSIX spec: when both fields are restricted, either match runs the job. When one is * it's ignored.

    Are day/month names supported?

    +

    Yes. Both numeric (0-6 for Sun-Sat) and name (sun, mon, tue…) forms work; case-insensitive.

    Does it show UTC or local time?

    +

    The 'Next executions' list renders in your browser's local time zone. If you need UTC, subtract your offset — or paste a few results into our Time Zone Converter.

    Why did my expression fail to parse?

    +

    The error message names the specific field or token. Most common cause: a 6-field expression (common on Quartz / Spring). Remove the seconds field.