Cron Expression Parser

Cron is a time-based job scheduler found in Unix-like operating systems. A cron expression is a string of five fields (minute, hour, day-of-month, month, day-of-week) that define a recurring schedule. Each field can be a single value, a comma-separated list, a range (1-5), or a step (*/15). The scheduler fires a job whenever the fields match the current wall-clock time — with one exception, below.

Day-of-month and day-of-week are ORed, not ANDed, whenever both are restricted. 0 0 13 * 5 does not mean "the 13th, but only on a Friday" — it means "the 13th or any Friday", around 64 runs a year rather than a couple. Every other pair of fields is ANDed, which is what makes this one easy to read wrongly. When either day field is * the question does not arise, and the other field simply applies.

Wildcards and steps make it easy to express common patterns: * matches every value in the field's range; */n matches every nth value starting from the minimum. For example, */5 in the minute field produces 0, 5, 10, … 55. A range with step like 0-30/10 yields 0, 10, 20, 30.

Timezone gotcha: cron runs in the server's local timezone unless the daemon is configured otherwise (e.g. via CRON_TZ or systemd's OnCalendar). This tool shows times in your browser's local timezone. When DST transitions occur, an hour may be skipped or repeated — check your platform's documentation for how it handles the ambiguity.

6-field cron (seconds as the first field) is supported by some schedulers (Quartz, Spring, AWS CloudWatch Events). This tool accepts a 6-field expression and treats the first field as seconds, though next-run calculations remain minute-granular.