Cron Checker

Cron Checker focuses on accuracy of cron expressions and reliable prediction of their schedules. It supports standard 5-field cron syntax and may accept a seconds field (optional) for higher-resolution expressions. Users include developers, systems engineers, and DevOps staff who configure recurring jobs on servers, cloud schedulers, or container orchestrators. The tool parses the input, validates each field against allowed ranges, and returns a structured result indicating validity and a list of upcoming run times. It also surfaces helpful diagnostics when a field is out of range or a named value is unrecognized. All computations are simulations; no tasks are executed.
Under the hood, the tool tokenizes the expression into minute/hour/day-of-month/month/day-of-week fields, applies timezone rules, and iteratively computes the next N occurrences from the given start time or now if absent. It uses ISO timestamps for outputs and produces an array of future datetimes in the selected zone. If a seconds field is present, the calculation adapts to per-second granularity. Timezone handling relies on IANA database; daylight saving shifts are accounted for in output times. The system flags ambiguous expressions (e.g., both DOM and DOW restricted) per cron semantics.
Use cases include validating deployment pipelines, diagnosing scheduled tasks in CI/CD, and teaching cron concepts. Unique value: timezone-aware, optional seconds field, immediate feedback on syntax and schedule preview, with a compact JSON-friendly output. Core features: syntax validation, next-run preview, range checks, error reporting, and export-ready results. Typical workflows: input expression and optionally a start time and timezone, request preview of next N occurrences, review results, and iterate.