Cron expression for every 90 minutes
Every 90 minutes, counted from midnight.
Next 10 runs
In Cron, worked out in your browser from the current time.
At a glance
- Runs
- 16 a day
- Gap between runs
- Always 1 hour 30 minutes
- Expressible in
- All six dialects
- Clock changes
- Affected in New York, London, Helsinki
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.
0 */3 * * * /path/to/command
30 1-23/3 * * * /path/to/command- Add all 2 lines to the crontab.
aws events put-rule --name every-90-minutes --schedule-expression "cron(0 0/3 * * ? *)"
aws events put-rule --name every-90-minutes --schedule-expression "cron(30 1/3 * * ? *)"- 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. - Create one rule per expression, each with the same target. A single
rate(90 minutes)also works, but it counts from when the rule is created, not from midnight.
CronScheduleBuilder.cronSchedule("0 0 0/3 * * ?")
CronScheduleBuilder.cronSchedule("0 30 1/3 * * ?")- The leading
0is 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. - Attach one
CronTriggerper expression to the same job.SimpleScheduleBuilder.repeatMinutelyForever(90)is the one-trigger alternative, counted from the trigger’s start time.
schedule: "0 */3 * * *"
schedule: "30 1-23/3 * * *"- A CronJob takes one schedule, so this needs 2 CronJobs sharing a job template.
- The controller stops starting a CronJob that has missed more than 100 schedules. At this rate that is 150 hours of downtime.
startingDeadlineSecondslimits how far back it counts.
- cron: '0 */3 * * *'
- cron: '30 1-23/3 * * *'- 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.
- List all 2 under
schedule:in one workflow.github.event.scheduletells a step which one fired.
[TimerTrigger("0 0 */3 * * *")]
[TimerTrigger("0 30 1/3 * * *")]- Six fields with seconds first, so the leading
0fires at the top of the minute. - A timer trigger takes one expression, so this needs 2 functions. On an App Service plan, the TimeSpan
01:30:00is the single-trigger alternative, measured between runs rather than from midnight.
About this schedule
No cron field can step by 90 minutes, because minutes stop at 59. Two lines do it: on the hour every third hour from midnight, and at half past every third hour from 01:30. Ninety minutes divides a day exactly, so there is no short gap at midnight.
Clock changes
Worked out by running each dialect’s engine through New York’s clock changes; it is affected in London, Helsinki too, at their own local hours.
| Dialect | Clocks go forward (02:00 becomes 03:00) | Clocks go back (02:00 becomes 01:00) |
|---|---|---|
| Cron | Not affected | 01:30 happens twice, and it runs both times |
| EventBridge Scheduler | Not affected | 01:30 happens twice, and it runs once, in the first pass |
| Quartz | Not affected | 01:30 happens twice, and it runs once, in the second pass |
| Kubernetes | Not affected | 01:30 happens twice, and it runs both times |
| GitHub | Not affected | 01:30 happens twice. GitHub doesn’t document whether it repeats; shown once here |
| Azure | Not affected | 01:30 happens twice, and it runs both times |
Cron follows the crontab man page; daemons differ, and cronie catches up skipped fixed-time jobs. EventBridge applies to Scheduler with a time zone; scheduled rules run in UTC and never see a clock change. Quartz is exact for 2.5.2. GitHub documents the forward case only.
Questions
- What is the cron expression for every 90 minutes?
- It takes 2 lines, used together:
0 */3 * * *,30 1-23/3 * * *in standard cron, Kubernetes and GitHub Actions. The other dialects differ:0 0/3 * * ? *,30 1/3 * * ? *in EventBridge;0 0 0/3 * * ?,0 30 1/3 * * ?in Quartz;0 0 */3 * * *,0 30 1/3 * * *in Azure. - Can one cron expression run every 90 minutes?
- No. The minute field stops at 59 and the hour field only takes whole hours, so a 90-minute step cannot be written in one line. Two lines, three hours apart and offset by 90 minutes, cover it exactly.
- What happens to this schedule when the clocks change?
- It depends on the scheduler. When clocks go forward in New York (02:00 becomes 03:00): Cron, EventBridge, Quartz, Kubernetes, GitHub and Azure: not affected. The table on this page also covers the autumn change.