CronCalc is a scheduling reference tool provided for general informational use. A few honest boundaries about what that does and doesn’t cover.

Predictions are not guarantees

The descriptions and next-run times follow standard POSIX/Vixie cron semantics as carefully as we can make them — but the authority for what your job does is the daemon that runs it. Cron implementations differ in the wild: Quartz ANDs the day fields where standard cron ORs them, some daemons honor CRON_TZ and some don’t, DST edge behavior varies, and managed platforms add their own rules. Before a schedule matters — a backup, a billing run, a deploy window — verify it on the system that will actually execute it.

The consequences of a schedule are yours

A cron line that fires at the wrong time, too often, or never can lose data, spam mailboxes, or hold a migration window open. The calculator helps you see what an expression means; whether it should run is a decision that stays with you. Test on a non-production crontab, and read debugging cron for the environmental reasons a correct schedule can still fail.

Articles are guidance, not runbooks

The guides — field reference, the OR trap, systemd timers — describe common patterns and platform differences. They aren’t a substitute for your own system’s man 5 crontab or man systemd.timer; where the text and your local documentation disagree, the local documentation is right for your box.

Advertising

The site may show third-party ads (e.g. Google AdSense) to cover hosting. Advertisers have no say in what the calculator outputs or what the guides recommend.

Liability

To the maximum extent permitted by law, CronCalc and its maintainers accept no liability for losses arising from use of this site — including missed or mistimed jobs, data loss and downtime. When a schedule matters, confirm it on the target system.