What times does every 4 hours run at?

Midnight, 4 AM, 8 AM, noon, 4 PM, and 8 PM — six evenly-spaced runs starting from hour 0.

Why is every 4 hours such a common default?

It divides the day into a manageable number of checkpoints (6) without the overhead of hourly runs, making it a practical middle ground for periodic maintenance and sync tasks across many platforms and tools.

How do I shift every-4-hours to start at 2 AM instead of midnight?

Use an explicit list instead of a step: 0 2,6,10,14,18,22 * * * keeps the same 4-hour spacing but starts at 2 AM.

Cron: Every 4 Hours

0 */4 * * * fires six times a day — midnight, 4 AM, 8 AM, noon, 4 PM, and 8 PM. Four is one of the most common hour-based intervals in production systems, striking a balance between the overhead of frequent polling and the staleness of once- or twice-daily jobs.

0 */4 * * *

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Examples & Variations

0 */4 * * *

Every 4 hours, all day

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0 8-20/4 * * *

Every 4 hours, 8 AM–8 PM only

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30 */4 * * *

Every 4 hours, offset to :30

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Common Mistakes

Assuming '4 hours' means 4 hours from whenever the job last ran — cron always anchors to midnight, so a manually-triggered run doesn't shift the schedule.
Running multiple unrelated 4-hour jobs all at :00 — six simultaneous invocations a day is enough to create a noticeable load spike if several heavy jobs share that exact schedule.
Not considering whether the underlying data actually changes on a 4-hour cadence — matching the job's frequency to the data's actual update rate avoids wasted work.

Best Practices

A dependable default for sync jobs, cache invalidation, and periodic reports where near-real-time freshness isn't required.
Offset the minute field (30 */4 * * * instead of 0 */4 * * *) if you need to avoid colliding with other jobs pinned to the top of the hour.
Six runs a day is frequent enough to catch problems within a reasonable window — pair with basic failure alerting for anything business-relevant.

Frequently Asked Questions

What times does every 4 hours run at?: Midnight, 4 AM, 8 AM, noon, 4 PM, and 8 PM — six evenly-spaced runs starting from hour 0.
Why is every 4 hours such a common default?: It divides the day into a manageable number of checkpoints (6) without the overhead of hourly runs, making it a practical middle ground for periodic maintenance and sync tasks across many platforms and tools.
How do I shift every-4-hours to start at 2 AM instead of midnight?: Use an explicit list instead of a step: 0 2,6,10,14,18,22 * * * keeps the same 4-hour spacing but starts at 2 AM.

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Cron: Every 3 Hours

The cron expression for every 3 hours is 0 */3 * * *, firing 8 times a day. See examples, mistakes, and best practices for this schedule.

Cron: Every 6 Hours

The cron expression for every 6 hours is 0 */6 * * *, firing 4 times a day. See examples, mistakes, and best practices for this schedule.

Cron: Every 8 Hours

The cron expression for every 8 hours is 0 */8 * * *, firing 3 times a day — matching a classic 8-hour shift pattern. See examples and best practices.