Cron Expression Parser

Parses a 5-field cron expression, explains each field, and lists the next 5 run times.

What this tool does

Translates an expression like 0 9 * * 1-5 into plain language: the allowed values for the minute, hour, day-of-month, month, and day-of-week fields, plus the next five concrete run times in your browser's local time zone. Seeing “next run” beats squinting at asterisks and slashes. Supports *, comma lists, ranges, / steps, and the JAN–DEC / SUN–SAT name aliases.

Typical use cases

Verify a schedule before committing it, instead of being woken at 3 a.m. by a misconfigured job; make sense of someone else's crontab when taking over a legacy system; debug “why didn't the job run” — pasting the expression here and comparing the expected run times usually reveals the problem immediately.

Caveats

The classic trap: when both day-of-month and day-of-week are restricted (neither is *), standard cron ORs them — 0 0 1 * 1 means “the 1st of the month, and also every Monday”, not “the 1st when it falls on a Monday”. Dialects differ too: standard crontab has 5 fields, Quartz adds seconds and year, systemd timers use another syntax entirely; this tool follows standard 5-field crontab. Actual execution uses the server's time zone, which may differ from the browser time zone shown here.