Cron Expression Parser & Explainer

Enter a standard 5-field cron expression to see what it means, validate each field and calculate upcoming execution times. OwnFormatters breaks down minute, hour, day, month and weekday values into a readable schedule.

Unix 5-Field Cron Parser & Schedule Calculator Workspace

Validate expressions against POSIX crontab standards, inspect field boundaries, review human-readable explanations, and calculate upcoming run dates in local time or UTC.

What is a Cron Expression?

A cron expression is a compact string format used by Unix, Linux, and modern job schedulers to define automated execution intervals. In standard Unix crontab specifications, an expression consists of exactly five space-separated fields representing Minute (0-59), Hour (0-23), Day of Month (1-31), Month (1-12), and Day of Week (0-6, where 0 is Sunday). When a schedule daemon evaluates the expression, it determines whether the current system timestamp satisfies all active field constraints.

The Standard 5-Field Format

Standard crontab follows a strict 5-column positional order:

* * * * *
┬ ┬ ┬ ┬ ┬
│ │ │ │ └─ Day of Week (0 - 6, 0 = Sun)
│ │ │ └─── Month (1 - 12)
│ │ └───── Day of Month (1 - 31)
│ └─────── Hour (0 - 23)
└───────── Minute (0 - 59)

Day of Month vs Day of Week Semantics

A critical distinction in standard POSIX crontab is the handling of day constraints. When both Day of Month and Day of Week are explicitly restricted (neither is an asterisk *), standard cron evaluates the condition as a logical OR union rather than an AND intersection. The job fires if either the calendar day matches OR the day of the week matches.

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