Field by field
*/30 * * * * reads: Every 30 minutes. That is 48 runs a day.
| Field | Value | Selects |
|---|---|---|
| Minute | */30 | every 30 minutes: 0 and 30 |
| Hour | * | every hour |
| Day of month | * | any day of the month |
| Month | * | every month |
| Day of week | * | any day of the week |
Worth knowing
- 48 runs a day, on the hour and the half hour.
30 * * * *is a different schedule: once an hour, at half past.
Variations
30 * * * *Once an hour, at half pastExplain it*/30 9-18 * * 1-5Every half hour during office hours on weekdaysExplain it
The same schedule elsewhere
crontab
*/30 * * * * /path/to/job.sh
Runs in the machine's local timezone. crontab -e to edit.
GitHub Actions
on:
schedule:
- cron: "*/30 * * * *"Always UTC. Nothing more often than every 5 minutes, and runs can start late when GitHub is busy.
Kubernetes CronJob
spec: schedule: "*/30 * * * *" timeZone: "Asia/Kolkata"
timeZone needs Kubernetes 1.27 or later; without it the controller's zone applies, usually UTC.
Spring @Scheduled
@Scheduled(cron = "0 */30 * * * *")
Six fields: seconds come first. Days are written as names, which Spring and cron read alike.
Quartz
0 0/30 * * * ?
One of day-of-month and day-of-week must be ?. Quartz counts days 1-7 from Sunday, so names are safer than numbers.
AWS EventBridge
cron(0/30 * * * ? *)
Six fields, the last one the year. UTC unless the schedule sets a timezone. Days count from Sunday, as in Quartz.
systemd timer
[Timer] OnCalendar=*-*-* *:00/30:00 Persistent=true
Persistent=true runs a job that was missed while the machine was off, once it is back.