`0 * * * *` — What does this cron expression mean?

0 * * * * is the hourly cron job, identical to @hourly. The single 0 in the minute field is the whole schedule: every hour, the job fires when the clock reads :00. That is simple, but it also means your job competes with every other hourly job on the same machine, cluster or CI provider in that one minute.

In plain English

0 * * * *

Run the job once every hour, exactly on the hour (minute 0): 00:00, 01:00, 02:00 … 23:00.

Frequency: 1 run per hour, 24 per day. cronstrue reads it as “Every hour”.

Open 0 * * * * in the Cron Builder

Field-by-field breakdown

Minute

0–59

Hour

0–23

Day of month

1–31

Month

1–12

Day of week

0–6

Minute0 — only at minute 0, the top of the hour.
Hour* — every hour, 0 through 23.
Day of month* — every day of the month.
Month* — every month.
Day of week* — every day of the week.

Next run times

Example: next 5 runs

Example: if it is Monday, 5 Jan 2026, 09:07 UTC, the next runs of 0 * * * * (UTC) are:

#1Mon, 5 Jan 2026, 10:00 UTCin 53 min
#2Mon, 5 Jan 2026, 11:00 UTCin 2h
#3Mon, 5 Jan 2026, 12:00 UTCin 3h
#4Mon, 5 Jan 2026, 13:00 UTCin 4h
#5Mon, 5 Jan 2026, 14:00 UTCin 5h

Live times from your current clock replace this example once the page loads. Cron uses the scheduler's timezone; most cloud servers, GitHub Actions and AWS EventBridge rules use UTC.

0 * * * * in Quartz, AWS, GitHub Actions, Kubernetes and systemd

Crontab (Linux / macOS)

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

Standard 5-field syntax used by Vixie cron, cronie, busybox crond and most libraries (node-cron, APScheduler, robfig/cron).

Quartz (6 and 7 fields)

0 0 * * * ?
0 0 * * * ? *

# Spring @Scheduled
@Scheduled(cron = "0 0 * * * *")

Generators such as CronMaker output 0 0 0/1 1/1 * ? * for “every hour”. It is the same schedule written verbosely: 0/1 is every hour from 0 and 1/1 is every day from the 1st.

AWS EventBridge

cron(0 * * * ? *)

# interval alternative
rate(1 hour)

Note the singular unit: rate(1 hour), not rate(1 hours). AWS rejects the plural when the value is 1.

GitHub Actions

on:
  schedule:
    # Every hour, evaluated in UTC
    - cron: '0 * * * *'

GitHub's documentation warns that load is highest at the start of every hour, and runs may be delayed or dropped. If “roughly hourly” is fine, prefer a random minute such as 23 * * * *.

Kubernetes CronJob

apiVersion: batch/v1
kind: CronJob
metadata:
  name: every-hour
spec:
  schedule: "0 * * * *"
  timeZone: "Etc/UTC"
  concurrencyPolicy: Forbid
  startingDeadlineSeconds: 600
  jobTemplate:
    spec:
      template:
        spec:
          restartPolicy: OnFailure
          containers:
            - name: job
              image: alpine:3.20
              command: ["/bin/sh", "-c", "echo running"]

Kubernetes accepts @hourly too. A 10-minute deadline keeps a late Job useful without risking a pile-up.

systemd timer

# /etc/systemd/system/myjob.timer
[Unit]
Description=Every hour

[Timer]
OnCalendar=hourly
Persistent=true

[Install]
WantedBy=timers.target

hourly means *-*-* *:00:00. Add RandomizedDelaySec=5min if many timers share the same host.

When to use every hour

Rolling up raw events into hourly aggregates.
Refreshing exchange rates, weather or other data that changes on an hourly cadence.
Running log shippers or upload jobs that batch an hour's worth of files.
Pruning temporary files and caches before they fill a small disk.

Common pitfalls with 0 * * * *

:00 is the most crowded minute everywhere

Hourly jobs from every team, every package and every tenant land on :00. On shared databases this produces an hourly latency spike; on CI providers it means queueing. Jenkins introduced the H symbol (H * * * *) for exactly this reason: it picks a stable pseudo-random minute per job. In plain cron, pick a minute yourself.

# Everyone's hourly job
0 * * * *

# Same frequency, off the crowded minute
23 * * * *

Hourly is not “60 minutes after the last run”

Cron fires at wall-clock :00. If the server is down from 10:58 to 11:02, the 11:00 run is lost, not delayed. If a run must not be skipped, use a scheduler that catches up (systemd Persistent=true, anacron) or make the next run process everything since the last success.

0 * * * * vs * 0 * * *

Swapping the first two fields changes everything: * 0 * * * runs every minute between 00:00 and 00:59, 60 times a day, and never at any other hour.

Related cron expressions

Every 15 minutes

*/15 * * * *

At minute 15 of every hour

15 * * * *

Every 4 hours

0 */4 * * *

Every 6 hours

0 */6 * * *

Need a different schedule? Paste 0 * * * * into the Cron Builder and edit it, browse all cron expressions, read the cron syntax guide or copy from the cron examples list.

Frequently Asked Questions

What does 0 * * * * mean in cron?▾

Once every hour at minute 0. The job runs at 00:00, 01:00, 02:00 and so on, 24 times a day. It is identical to @hourly.

What is 0 0 0/1 1/1 * ? * in cron?▾

It is a 7-field Quartz expression (seconds, minutes, hours, day-of-month, month, day-of-week, year) meaning every hour on the hour, the same as 0 * * * * in crontab. Tools such as CronMaker generate this verbose form; 0 0 * * * ? is the shorter Quartz equivalent.

How do I write an hourly cron job for AWS?▾

Use cron(0 * * * ? *) to run at the top of every hour UTC, or rate(1 hour) to run every 60 minutes from when the rule was created.

0 * * * * — What does this cron expression mean?