What is the cron expression for every 4 hours?

The cron expression for every 4 hours is 0 */4 * * *. This schedule runs 6 times per day.

How do I set up a cron job for every 4 hours?

Open your crontab with 'crontab -e' and add a line starting with '0 */4 * * *' followed by the command you want to run. For example: 0 */4 * * * /path/to/script.sh

Cron Expression for Every 4 Hours

Q: What does each field in 0 */4 * * * mean?

A cron expression has 5 fields: minute (0), hour (*/4), day of month (*), month (*), and day of week (*). In 0 */4 * * *: 0 — at the top of the hour; */4 — every 4th hour (0, 4, 8, 12, 16, 20).

0 */4 * * *

Expression Breakdown

The cron expression 0 */4 * * * schedules a job to run every 4 hours. A standard cron expression consists of five fields representing minute, hour, day of month, month, and day of week. Here is what each field means in this expression:

Minute	`0` — at the top of the hour
Hour	`*/4` — every 4th hour (0, 4, 8, 12, 16, 20)
Day of Month	`*` — every day of the month
Month	`*` — every month
Day of Week	`*` — every day of the week

This schedule runs 6 times per day (0.25 times per hour), which amounts to 42 times per week and approximately 180 times per month.

Next 5 Run Times

Starting from April 11, 2026 00:00 UTC, the next five executions are:

2026-04-11T00:00:00Z — Sat, 11 Apr 2026 00:00:00 GMT
2026-04-11T04:00:00Z — Sat, 11 Apr 2026 04:00:00 GMT
2026-04-11T08:00:00Z — Sat, 11 Apr 2026 08:00:00 GMT
2026-04-11T12:00:00Z — Sat, 11 Apr 2026 12:00:00 GMT
2026-04-11T16:00:00Z — Sat, 11 Apr 2026 16:00:00 GMT

Common Use Cases

Running a task every 4 hours is a popular cron schedule. Here are some typical applications:

CDN cache: CDN cache purge and content refresh
Incremental database: Incremental database backup snapshots
API rate: API rate limit reset monitoring
Scheduled search: Scheduled search index rebuilds for large datasets

Code Examples

Linux / macOS Crontab

# Open crontab editor
crontab -e

# Add this line to run your script every 4 hours
0 */4 * * * /usr/local/bin/my-task.sh

# With logging
0 */4 * * * /usr/local/bin/my-task.sh >> /var/log/my-task.log 2>&1

Python (schedule library alternative)

# Using APScheduler with cron trigger
from apscheduler.schedulers.blocking import BlockingScheduler
from apscheduler.triggers.cron import CronTrigger

scheduler = BlockingScheduler()
trigger = CronTrigger.from_crontab("0 */4 * * *")
scheduler.add_job(my_function, trigger)
scheduler.start()

JavaScript (Node.js with node-cron)

const cron = require('node-cron');

// Run task every 4 hours
cron.schedule('0 */4 * * *', () => {
  console.log('Task running at', new Date().toISOString());
  // Your task logic here
});

Frequently Asked Questions

What does each field in 0 */4 * * * mean?

A cron expression has five fields separated by spaces: minute (0-59), hour (0-23), day of month (1-31), month (1-12), and day of week (0-7, where 0 and 7 are Sunday). The */n syntax means "every nth interval." In 0 */4 * * *, the fields are: 0 — at the top of the hour; */4 — every 4th hour (0, 4, 8, 12, 16, 20); * — every day of the month.

How do I verify that 0 */4 * * * is correct?

Use the EpochPilot Cron Expression Builder to paste your expression and see the next run times visually. You can also use the crontab -l command to list your current crontab entries, or test with a simple echo command: 0 */4 * * * echo "test" >> /tmp/cron-test.log.

What timezone does cron use?

By default, cron uses the system timezone configured on your server. On most cloud servers this is UTC. You can check your system timezone with timedatectl on Linux or date +%Z. Some cron implementations (like Kubernetes CronJobs) let you specify a timezone explicitly. Always verify your server's timezone to ensure jobs run at the expected times.

Try the Cron Expression Builder to create and test cron schedules.