Cron Expression Generator
Build a crontab schedule from dropdowns — minute, hour, day, month, weekday — with a plain-English readout and common presets.
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The Five Fields
A cron expression is minute · hour · day-of-month · month · day-of-week, left to right. * means "every"; */15 every 15 units; 1,15 a list; 1-5 a range. So 0 9 * * 1-5 runs 09:00 on weekdays, */10 * * * * every 10 minutes, 0 0 1 * * midnight on the 1st of each month.
Gotchas: day-of-month and day-of-week are OR-ed when both are restricted (a surprise to most); weekday 0 and 7 both mean Sunday; times run in the server's timezone. Cloud schedulers (GitHub Actions, AWS, Kubernetes CronJob) use the same five fields, some with extensions.
Frequently Asked Questions
How do I run something every 30 seconds?
Classic cron's smallest unit is a minute. The common workaround is two entries: one plain, one with `sleep 30 &&` before the command — or use systemd timers, which support seconds.
Why did my 9:00 job run at a strange hour?
Almost always timezone: crontab runs in the server's local time (often UTC on cloud boxes). Check with `date` on the host, or set CRON_TZ where supported.
How do I test an expression safely?
Point it at a logging command first: `* * * * * date >> /tmp/cron-test.log`, confirm the cadence, then swap in the real command. Also confirm the crontab user has the needed PATH — cron's environment is minimal.
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Cron Expression Generator