Cron Expression Tester

Paste your cron expression into the input — e.g. '*/15 9-17 * * 1-5' — and hit Parse. The tester validates each field, explains the expression in plain English, and shows the next 10 scheduled run times with their day-of-week labels.

The 5 fields (left to right) are: Minute (0–59), Hour (0–23), Day of Month (1–31), Month (1–12 or JAN–DEC), and Day of Week (0–6 where 0=Sunday, or SUN–SAT). Use * for 'any', */n for 'every n units', ranges like 1-5, and comma-separated lists like 1,3,5.

Linux cron uses 5-field syntax (minute hour day month weekday). GitHub Actions also uses 5-field POSIX cron in UTC. AWS EventBridge uses 6-field syntax with an optional seconds field. This tester uses standard 5-field cron compatible with Linux cron, GitHub Actions, and most schedulers.

Common issues: (1) Server timezone — cron runs in local server time, not your local time. Check with 'crontab -l' and 'date'. (2) The expression '0 9 * * 1-5' runs at 9:00 on weekdays, but '0 9 * * 1,2,3,4,5' does the same. (3) Day-of-month and day-of-week fields are ORed in most cron implementations, not ANDed.

Use '*/15 9-17 * * 1-5'. This runs every 15 minutes (0, 15, 30, 45) during hours 9–17 on weekdays (Monday–Friday). Note: it will fire at 9:00, 9:15, 9:30, ... 17:45 — including the :00 and :45 marks within hour 17.

Standard cron minimum is 1 minute ('* * * * *' runs every minute). For sub-minute scheduling, use a loop in your script, systemd timers with AccuracySec, or cloud schedulers like AWS EventBridge with rate expressions (rate(30 seconds)).