DevToolsmith

Cron Job Every 45 Minutes

Standard cron can’t express “Every 45 minutes” in a single expression. Here is the closest schedule, */45 * * * *, plus the workaround that fills the gap and copy-ready examples.

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Cron schedule

Schedule time zone

UTC

Closest cron expression

*/45 * * * *

At 0 and 45 minutes past the hour. On its own, it runs 48 times a day, 17,520 times a year.

This is a classic cron trap. */45 in the minute field means “minutes divisible by 45”, which is only :00 and :45. So */45 * * * * runs at 10:00, 10:45, 11:00, 11:45, with gaps that alternate between 45 and 15 minutes. Steps restart every hour, so no single cron line runs every 45 minutes.

Workaround: run a job every 45 minutes

Run every 15 minutes and let the command skip two out of three runs, based on the number of minutes since the Unix epoch. In a crontab, % must be escaped as \%.

crontab
*/15 * * * * [ $(( $(date +\%s) / 60 \% 45 )) -lt 15 ] && /usr/local/bin/job.sh

The same idea works on every scheduler below: keep the base schedule and put the check at the start of the job’s command or script.

Field by field

FieldValueMatches
minute */45 0, 45
hour * every value
day of month * every value
month * every value
day of week * every value

Examples

crontab

Run crontab -e and add:

*/45 * * * * /usr/local/bin/job.sh >> /var/log/job.log 2>&1

For the exact schedule, use the workaround line above instead.

Kubernetes CronJob

apiVersion: batch/v1
kind: CronJob
metadata:
  name: my-job
spec:
  schedule: "*/45 * * * *"
  timeZone: "Etc/UTC"          # Kubernetes 1.27+
  concurrencyPolicy: Forbid    # skip a run if the last one is still going
  jobTemplate:
    spec:
      template:
        spec:
          containers:
            - name: job
              image: ghcr.io/acme/job:1.0
          restartPolicy: OnFailure

GitHub Actions

on:
  schedule:
    - cron: '*/45 * * * *'   # UTC

GitHub evaluates schedules in UTC, and runs can start several minutes late at busy times.

systemd timer

# /etc/systemd/system/job.timer
[Unit]
Description=Run job.service every 45 minutes

[Timer]
OnCalendar=*-*-* *:00,45:00
Persistent=true

[Install]
WantedBy=timers.target

Enable it with systemctl enable --now job.timer, and check the next runs with systemd-analyze calendar "*-*-* *:00,45:00". Persistent=true runs a missed job after downtime, which cron can’t do.

AWS EventBridge

cron(0,45 * * * ? *)

EventBridge cron has six fields (the last is the year), uses ? in either the day-of-month or the day-of-week field, and numbers weekdays from 1 (Sunday) to 7. Rules run in UTC; EventBridge Scheduler also accepts a time zone.

Similar schedules: every few minutes

Have a different schedule? Paste any expression into the Cron Expression Generator, or browse all cron examples.

Sources

Spotted a mistake? Email hello@devtoolsmith.com and we’ll fix it.

Frequently asked questions

How do I run a cron job every 45 minutes?

No single standard cron expression does this exactly. This is a classic cron trap. */45 in the minute field means “minutes divisible by 45”, which is only :00 and :45. So */45 * * * * runs at 10:00, 10:45, 11:00, 11:45, with gaps that alternate between 45 and 15 minutes. Steps restart every hour, so no single cron line runs every 45 minutes. Run every 15 minutes and let the command skip two out of three runs, based on the number of minutes since the Unix epoch. In a crontab, % must be escaped as \%. */15 * * * * [ $(( $(date +\%s) / 60 \% 45 )) -lt 15 ] && /usr/local/bin/job.sh