Cron Atlas

Cron expression for every 12 hours

0 */12 * * *
minute0
hourevery 12
day of monthevery day
monthevery month
day of weekany weekday

At 00:00 and 12:00.

Next 10 runs

In Cron, worked out in your browser from the current time.

At a glance

Runs
2 a day
Gap between runs
Always 12 hours
Expressible in
All six dialects
Clock changes
No effect in the zones checked

Open in the tester

In each dialect

Every expression here is generated by the tester’s own engine and checked run for run against the others, so “Exact” means the same clock times in the same zone. Each one links to the tester.

Cron
0 */12 * * *
0 */12 * * * /path/to/command
  • Runs in the machine’s time zone. cronie also reads a CRON_TZ= line above the entry; other crons may not.
Exact
EventBridge
0 0,12 * * ? *
aws events put-rule --name every-12-hours --schedule-expression "cron(0 0,12 * * ? *)"
  • Wrap it in cron(…). Day of week is ? because day of month already holds *, and a * in both is rejected. The final * is the required year field.
  • rate(12 hours) is the interval alternative. It counts from when the rule is created, so runs will not line up with the clock the way the cron form does.
  • Scheduled rules always run in UTC. For local times, create it in EventBridge Scheduler with --schedule-expression-timezone.
Exact
Quartz
0 0 0,12 * * ?
CronScheduleBuilder.cronSchedule("0 0 0,12 * * ?")
  • The leading 0 is the seconds field, so it fires at the top of the minute. Day of week is ? because day of month already holds *, and a * in both is rejected. The optional year is left off.
  • Uses the JVM’s default zone unless the trigger sets one with inTimeZone.
Exact
Kubernetes
0 */12 * * *
schedule: "0 */12 * * *"
  • Without timeZone under spec, these times are in the kube-controller-manager’s zone. A CRON_TZ= prefix in the schedule fails validation.
Exact
GitHub
0 */12 * * *
- cron: '0 */12 * * *'
  • GitHub warns that schedules can be delayed at high load, which includes the start of every hour, and that some queued jobs may be dropped. A different minute reduces the risk.
  • Times are UTC unless you add timezone: beside cron, with an IANA name.
Exact
Azure
0 0 0,12 * * *
[TimerTrigger("0 0 0,12 * * *")]
  • Six fields with seconds first, so the leading 0 fires at the top of the minute.
  • UTC unless the app sets WEBSITE_TIME_ZONE, which Linux Consumption and Flex Consumption plans do not support.
Exact

About this schedule

Midnight and noon. For a different pair of times twelve hours apart, list the hours instead, for example 0 9,21 * * *. For two unevenly spaced times, see the twice-a-day page.

Clock changes

None of these times falls in the hour that clocks skip or repeat in New York, London, Berlin, Helsinki or Sydney, so every dialect runs it normally all year there. Zones that change clocks at other hours can still differ.

Questions

What is the cron expression for every 12 hours?
0 */12 * * * in standard cron, Kubernetes and GitHub Actions. The other dialects differ: 0 0,12 * * ? * in EventBridge; 0 0 0,12 * * ? in Quartz; 0 0 0,12 * * * in Azure.
Does 0 */12 * * * count from when the job is created?
No. It matches clock times: 00:00, 12:00 and so on, whenever it was created. EventBridge’s rate() form is the one that counts from creation instead.
Which time zone does it run in?
It depends on the scheduler. GitHub Actions, EventBridge rules and Azure use UTC unless you set a zone (timezone, EventBridge Scheduler’s --schedule-expression-timezone, WEBSITE_TIME_ZONE). Kubernetes uses .spec.timeZone or the controller manager’s zone, Quartz the JVM’s zone or inTimeZone, and cron the machine’s zone or CRON_TZ.

More schedules