Cron expression for every 6 hours

Free

0 */6 * * * - Every 6 hours, on the hour.

Field by field

0 */6 * * * reads: Every 6 hours, on the hour. That is 4 runs a day.

What each field of 0 */6 * * * selects
FieldValueSelects
Minute00
Hour*/6every 6 hours: 00:00, 06:00, 12:00 and 18:00
Day of month*any day of the month
Month*every month
Day of week*any day of the week

Worth knowing

  • Four runs a day, at midnight, 06:00, noon and 18:00 in the timezone the scheduler uses.
  • On a server set to UTC those are 05:30, 11:30, 17:30 and 23:30 in India - check the timezone before promising anyone a time.

Variations

  • 0 3-23/6 * * *Every 6 hours, starting at 03:00Explain it
  • 0 0,6,12,18 * * *The same schedule, written as a listExplain it

The same schedule elsewhere

crontab

0 */6 * * * /path/to/job.sh

Runs in the machine's local timezone. crontab -e to edit.

GitHub Actions

on:
  schedule:
    - cron: "0 */6 * * *"

Always UTC. Nothing more often than every 5 minutes, and runs can start late when GitHub is busy.

Kubernetes CronJob

spec:
  schedule: "0 */6 * * *"
  timeZone: "Asia/Kolkata"

timeZone needs Kubernetes 1.27 or later; without it the controller's zone applies, usually UTC.

Spring @Scheduled

@Scheduled(cron = "0 0 */6 * * *")

Six fields: seconds come first. Days are written as names, which Spring and cron read alike.

Quartz

0 0 0/6 * * ?

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 0/6 * * ? *)

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=*-*-* 00/6:00:00
Persistent=true

Persistent=true runs a job that was missed while the machine was off, once it is back.