Cron expression for twice a day

0 9,21 * * *

At 09:00 and 21:00, every day.

A list in the hour field runs the job at each listed hour: here 09:00 and 21:00. Use 0 */12 * * * for midnight and noon.

Try it and tweak it

Change any field below and the preview updates. Set the time zone to match your server.

✓ Valid cron

At 09:00 and 21:00, every day.

Next 10 runs

Calculating in your browser…

Times are computed in your browser for the selected zone and are informational. The server that runs the job uses its own zone (often UTC) and cron flavour, so verify there.

Same schedule in other dialects

Unix crontab0 9,21 * * *
Quartz0 0 9,21 * * ?
Spring @Scheduled0 0 9,21 * * ?
AWS EventBridgecron(0 9,21 * * ? *)

Add it to your crontab

  1. Open your crontab with crontab -e.
  2. Add one line: 0 9,21 * * * /full/path/to/command >> /var/log/job.log 2>&1
  3. Save and exit. Cron reloads automatically; confirm with crontab -l.

Need the output silenced, a lock against overlapping runs or a system crontab user column? The generator’s full crontab line builder writes it for you. Already have a crontab? Paste it into the crontab parser to check every job.

Variations

0 */12 * * *Midnight and noon
30 8,17 * * 1-508:30 and 17:30 on weekdays

In other schedulers

crontab line0 9,21 * * * /path/to/command
Quartz0 0 9,21 * * ?
Spring@Scheduled(cron = "0 0 9,21 * * ?")
AWS EventBridgecron(0 9,21 * * ? *)
GitHub Actions- cron: '0 9,21 * * *' (UTC)
Kubernetesschedule: "0 9,21 * * *"

Questions

What is the cron expression for twice a day?
0 9,21 * * *. At 09:00 and 21:00, every day.
How do I write it in Quartz or Spring?
Add a seconds field and use "?" for the unused day field: 0 0 9,21 * * ?. In Spring: @Scheduled(cron = "0 0 9,21 * * ?").
What is the AWS EventBridge version?
cron(0 9,21 * * ? *). AWS uses six fields with a year at the end and needs "?" in one of the day fields.
How do I set up a cron job to run twice a day?
Run crontab -e, add the line "0 9,21 * * * /full/path/to/command >> /var/log/job.log 2>&1" and save. Use absolute paths, because cron runs with a minimal PATH. Check it with crontab -l.
Which time zone will it use?
The time zone of the machine or service running cron. GitHub Actions and Vercel use UTC; Kubernetes uses spec.timeZone if set. The preview above lets you pick a zone.