Cron every odd hour: the expression, explained, in Docker

The cron expression for “every odd hour” is 0 1-23/2 * * *. This page shows what each field does, the next five times it will fire, the mistake most people make with it, and a working Docker example you can paste.

The expression

0 1-23/2 * * *

Field	Value	Meaning
minute	0	exactly 0
hour	1-23/2	every 2 hours, from 1 to 23
day of month	*	every day of month
month	*	every month
day of week	*	every day of week

Next five runs (UTC, from now)

2026-09-18 01:00 UTC
2026-09-18 03:00 UTC
2026-09-18 05:00 UTC
2026-09-18 07:00 UTC
2026-09-18 09:00 UTC

Mistakes people make with this schedule

Writing "*/2" and expecting odd hours. Steps count from 0, so "*/2" is even hours; "1-23/2" starts the step at 1 instead.
Assuming the server clock is your clock. Cron runs in the machine’s timezone unless the runtime says otherwise; the examples here are UTC.
No lock around a job that might overlap itself, and no alert when it silently stops. That second one is what Supercrontab is for.

Run it in your stack

Linux crontab Laravel WordPress Next.js / Vercel Node.js Python Docker GitHub Actions

# Dockerfile
RUN apk add --no-cache curl
RUN echo '0 1-23/2 * * * curl -fsS http://app:3000/cron/run' > /etc/crontabs/root
CMD ["crond", "-f", "-l", "2"]

Or skip the sidecar: expose the route and let Supercrontab call it.

Questions

Does 0 1-23/2 * * * run in my local time?

Only if the scheduler is configured for it. crontab uses the system timezone; Vercel and GitHub Actions always use UTC; Laravel and node-cron take a timezone option. In Supercrontab the timezone is a field on the job.

What if the previous run is still going?

Classic cron starts the next run anyway. Add a lock (flock on Linux, withoutOverlapping() in Laravel) or let Supercrontab skip the tick while the previous request is open.

Is there a shorter way to write this?

No. The five-field form is the shortest portable version.