What should I watch out for when running a cron job every 45 minutes?

This is the famous lie: */45 does NOT run every 45 minutes. Cron evaluates the minute field per-hour, so */45 * * * * fires at :00 and :45, then resets at the new hour — giving you a 45-minute gap followed by a 15-minute gap, not a true 45-minute interval. Confirm by listing the fire times before you trust it. A real 45-minute cadence needs a different mechanism. Standard cron can't express 'every 45 minutes' because 45 doesn't divide 60; use a systemd timer with OnUnitActiveSec=45min, or have the script sleep/re-arm itself, or compute it with an at chain — don't fake it with */45.

Cron expression for Every 45 minutes

Q: What is the cron expression for every 45 minutes?

The cron expression for every 45 minutes is "*/45 * * * *". Runs every 45 minutes, around the clock (fires at :00 and :45 each hour — standard cron can't do a true 45-minute interval).

*/45 * * * *

Runs every 45 minutes, around the clock (fires at :00 and :45 each hour — standard cron can't do a true 45-minute interval).

Next 5 runs (your local time)

These are shown in your browser’s timezone. The job itself runs in the scheduler’s timezone — often UTC — so the real run time can differ.

What people actually schedule with `/45 * * *`

A heartbeat or keep-alive ping where the exact cadence doesn't matter and you just want it 'roughly every 45 min'
A medium-weight report refresh you've decided is fine to run on an uneven rhythm rather than locking to the clock
Throttling a batch against a partner system that publishes guidance like 'no more than ~30 calls/day'

Use `/45 * * *` on your platform

It’s the same 5-field expression everywhere — what changes is where you put it and which timezone it runs in.

Linux / crontab

*/45 * * * * /path/to/your-command

Runs in the server’s local timezone — check it with timedatectl. Full field reference: crontab(5) man page.

GitHub Actions

on:
  schedule:
    - cron: "*/45 * * * *"

GitHub Actions always runs scheduled jobs in UTC — there is no timezone setting, and runs can be delayed under load (official docs).

Kubernetes CronJob

spec:
  schedule: "*/45 * * * *"

Defaults to UTC. Set spec.timeZone (Kubernetes 1.27+) for a specific zone — see the CronJob docs.

Quartz / Spring `@Scheduled`

Quartz uses 6 fields (seconds first): 0 */45 * * * *. Watch out: Quartz day-of-week is 1=SUN … 7=SAT (not 0–6), and day-of-month / day-of-week use ? — double-check if your schedule touches those fields (Quartz cron reference).

Gotchas with every 45 minutes schedules

This is the famous lie: */45 does NOT run every 45 minutes. Cron evaluates the minute field per-hour, so */45 * * * * fires at :00 and :45, then resets at the new hour — giving you a 45-minute gap followed by a 15-minute gap, not a true 45-minute interval. Confirm by listing the fire times before you trust it.
A real 45-minute cadence needs a different mechanism. Standard cron can't express 'every 45 minutes' because 45 doesn't divide 60; use a systemd timer with OnUnitActiveSec=45min, or have the script sleep/re-arm itself, or compute it with an at chain — don't fake it with */45.
The uneven gap breaks rate-limit math. If you chose 45 minutes to stay under a quota, the real pattern (two runs 15 min apart at the hour turnover) can burst two calls close together and trip a sliding-window limiter — budget for the :45→:00 short gap, not the average.

Will you know if this job silently fails?

Cron jobs fail quietly — a server reboots, a path changes, or an error code is ignored — and nobody notices until the data is missing. A cron monitor (a dead-man’s-switch) alerts you when a scheduled job does not check in on time.

Monitor your cron jobs with UptimeRobot →

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Is `/45 * * *` the right schedule?

If you genuinely need an interval cron can honor, step to every 30 minutes or every hour — both divide 60 and fire on a true fixed cadence, unlike the */45 pattern that only pretends to.

Or use the interactive cron generator & explainer, read the complete cron syntax guide, or pick another common schedule: