Regex and cron

Cron Expression for Every 3 Hours

At minute 0 of every third hour (00:00, 03:00, 06:00 … 21:00), every day. Copy it, check the next runs in your time zone and grab a snippet for your platform.

  • Free foreverNo trial, no paywall, no usage limits.
  • No sign-upOpen the page and start. We never ask for an email to use a tool.
  • PrivateEverything runs in your browser. Your input is never uploaded or stored on our servers.
  • Works offlineOnce the page has loaded, the tool keeps working without a connection.

Cron expression

0 */3 * * *
Customize
0minuteMinute: at minute 0 (on the hour)*/3hourHour: every 3 hours: 00:00, 03:00, 06:00 … 21:00*day (month)Day of month: every day of the month*monthMonth: every month*day (week)Day of week: every day of the week

At minute 0 of every third hour (00:00, 03:00, 06:00 … 21:00), every day.

Time zone
Run times, the week view and the snippets use this zone. It starts as your device's zone.
Show times as 9:00 AM instead of 09:00.

Next runs

Each run in your selected time zone, with the same moment in UTC. Daylight saving changes follow cronie, the cron on most Linux servers.
Copy run times (ISO 8601)

Next 7 days

Each square is one hour of local time in your selected zone. Darker squares have more runs. Daylight saving changes are not drawn.

Use it on your platform

Copy-ready config for each scheduler. Dialects differ: some only run in UTC, some can't do seconds, Cloudflare and AWS number weekdays from 1 = Sunday. The snippet handles the conversion and says what changed.
A line for crontab -e on Linux or macOS (Vixie cron, cronie).on.schedule for a workflow, with the timezone field GitHub added in March 2026 (UTC when omitted).A CronJob manifest with the timeZone field (Kubernetes 1.27+).Cron Triggers in wrangler.toml for a Worker. Runs in UTC and numbers weekdays from 1 = Sunday.crons in vercel.json plus the route it calls. Runs in UTC.EventBridge Scheduler (any time zone, recommended by AWS) and a legacy EventBridge scheduled rule (UTC).A .timer unit with OnCalendar=, the systemd replacement for cron.
Runs as writtenRuns in your time zone
crontab -e
Copy crontab -eDownload my-job.crontab
# ┌───────────── minute (0–59)
# │ ┌─────────── hour (0–23)
# │ │ ┌───────── day of month (1–31)
# │ │ │ ┌─────── month (1–12)
# │ │ │ │ ┌───── day of week (0–6, Sunday = 0)
# │ │ │ │ │
# * * * * *  command
CRON_TZ=UTC
0 */3 * * *  /path/to/my-job.sh >> /var/log/my-job.log 2>&1
  • CRON_TZ=UTC is honored by cronie (Fedora, RHEL, Arch). Other cron daemons ignore it and use the server's time zone, so check timedatectl first.
  • Edit with crontab -e. Cron starts the next run even if the last one is still going; wrap the command in flock -n /tmp/my-job.lock to prevent overlaps.

Need scheduled jobs, queues and monitoring that never miss a run? Talk to our team

Quick answer

The cron expression for every 3 hours is 0 */3 * * *. The */3 step in the hour field matches 0, 3, 6, 9, 12, 15, 18 and 21, and the 0 in the minute field runs the job at the top of each of those hours. That is 8 runs a day, evenly spaced because 24 divides by 3.

  • Live next runs
  • Any time zone
  • Field-by-field breakdown
  • Seven platform snippets
  • Daylight saving aware

How to use this schedule

  1. 1Copy 0 */3 * * * with the Copy expression button.
  2. 2Check Next runs in your time zone to confirm it fires when you expect, including around daylight saving changes.
  3. 3Pick your platform under Use it on your platform and copy the ready-made crontab line, workflow, manifest or timer.
  4. 4Need a different time or day? Click Customize to open it in the cron expression generator and change any field.

What does 0 */3 * * * mean?

The hour step */3 starts at 0 and keeps every third hour, giving eight values. Since 24 is a multiple of 3, the last gap (21:00 to midnight) is also three hours, so the rhythm never stutters. Compare 0 */5 * * *, which runs at 20:00 and then again at 00:00 after only four hours.

There are exactly three ways to place an every-3-hours schedule on the clock, one for each starting hour:

ExpressionRuns at
0 */3 * * *00, 03, 06, 09, 12, 15, 18, 21
0 1-23/3 * * *01, 04, 07, 10, 13, 16, 19, 22
0 2-23/3 * * *02, 05, 08, 11, 14, 17, 20, 23

Pick the phase that suits the people or systems on the other end. The third row, for example, hits 08:00, 11:00, 14:00 and 17:00, four checkpoints that fall neatly across a working day.

When is every 3 hours a good fit?

Eight runs a day is a common rhythm for work that should stay reasonably fresh without running constantly: importing price or stock feeds, refreshing exchange rates, snapshotting a fast-changing but non-critical database, or re-checking failed webhooks.

Keep daylight saving time in mind if the schedule runs in a local zone. In America/New_York, the March night jumps from 02:00 straight to 03:00, so the gap between the 00:00 and 03:00 runs is only two real hours. In November the 01:00 hour repeats and that same gap stretches to four real hours. A job that assumes "three hours since the last run" will under- or over-collect on those days; store the timestamp of the last successful run instead.

Shorter intervals live at every 2 hours; if a few runs a day are enough, every 6 hours halves the count.

What does each field in 0 */3 * * * mean?

FieldValueAllowedMeaning
Minute00–59at minute 0 (on the hour)
Hour*/30–23every 3 hours: 00:00, 03:00, 06:00 … 21:00
Day of month*1–31every day of the month
Month*1–12, JAN–DECevery month
Day of week*0–7 (0 and 7 are Sunday), SUN–SATevery day of the week

Read together: At minute 0 of every third hour (00:00, 03:00, 06:00 … 21:00), every day.

How do I adjust 0 */3 * * * to my own schedule?

Small edits to 0 */3 * * * cover most real-world needs:

ExpressionWhat it does
0 1-23/3 * * *Every 3 hours starting at 01:00 (01:00, 04:00 … 22:00)
0 2-23/3 * * *Every 3 hours starting at 02:00, hitting 08:00, 11:00, 14:00 and 17:00
30 */3 * * *Every 3 hours at half past (00:30, 03:30 … 21:30)
0 6-21/3 * * *Every 3 hours from 06:00 to 21:00 only
0 */3 * * 1-5Every 3 hours on weekdays

Need something else? Click Customize at the top of the page to open this schedule in the cron expression generator and change any field.

Related schedules: Every 2 hours · Every 4 hours · Every 6 hours · Every hour

Browse all schedules in the cron schedule library.

How do I run 0 */3 * * * in crontab, GitHub Actions, Kubernetes and the cloud?

PlatformWrite it asTime zone
Linux crontab0 */3 * * *Server's time zone; CRON_TZ= in cronie
GitHub Actions- cron: "0 */3 * * *"UTC by default; add timezone: (IANA name)
Kubernetes CronJobschedule: "0 */3 * * *"Set timeZone: (1.27+)
Cloudflare Workers0 */3 * * *UTC only; numbers weekdays from 1 = Sunday, so use names
Vercel Cron Jobs0 */3 * * *UTC only; more than once a day needs Pro (Hobby: once a day)
AWS EventBridge Schedulercron(0 */3 * * ? *)Takes a time zone; legacy scheduled rules are UTC only
systemd timerOnCalendar=*-*-* 0/3:00:00Add a zone after the time, e.g. Europe/London

In a crontab (crontab -e), the full line looks like this:

0 */3 * * *  /path/to/job.sh >> /var/log/job.log 2>&1

The live panel at the top of the page builds complete, copy-ready files for each platform (workflow, CronJob manifest, wrangler.toml, vercel.json, AWS CLI and systemd units) and can shift the schedule to UTC for platforms that need it.

What can go wrong with 0 */3 * * *?

  • */3 * * * * is every 3 minutes. For every 3 hours the step goes in the hour field and the minute needs a fixed value.
  • On daylight saving days in a local time zone the spacing changes: in America/New_York the gap from 00:00 to 03:00 is two real hours in March and four in November.
  • Every-3-hours jobs are often long (backups, catalog imports). If one can exceed three hours, wrap it in flock -n /tmp/job.lock your-command to skip the next start instead of doubling up.
  • If the job notifies people, check which runs land at night for them: 03:00 UTC is 23:00 the previous evening in New York during daylight time.
  • In a zone with daylight saving time, a schedule with * in the minute or hour field follows the wall clock: the spring-forward night loses an hour of runs and the fall-back night repeats one. Servers on UTC never see this.

Frequently asked questions

8 times: at 00:00, 03:00, 06:00, 09:00, 12:00, 15:00, 18:00 and 21:00.
Start the hour range at 1: 0 1-23/3 * * * runs at 01:00, 04:00, 07:00, 10:00, 13:00, 16:00, 19:00 and 22:00.
No. The step counts from hour 0, so the runs are always at the same eight clock times, no matter when you saved the crontab.
Yes. The step is shorthand for that list of hours, and both run at minute 0.

Last updated by the Playxoft engineering team.

From the engineers who built this tool

Need scheduled jobs that never miss a run?

Cron is the easy part. Retries, overlapping runs, time zones, queues and alerts when a job silently stops are where schedules break. We build background job systems you can trust, and we will review your setup for free.

Get a free job-scheduling reviewSee backend services

More free tools

See all tools

Regex Tester

Test regex live with highlighted matches, plain-English explanations and code export.

Open tool

Cron Expression Generator

New

Build and explain cron schedules, see the next runs in any time zone, copy platform snippets.

Open tool

SQL Formatter

Beautify or minify SQL in 12 dialects, with keyword case, indent and line:column errors.

Open tool

cURL to Python Converter

New

Convert cURL commands into Python requests or httpx code with params, json, files and auth.

Open tool

cURL to Fetch Converter

New

Turn any cURL command into JavaScript fetch() code with headers, JSON, forms and auth.

Open tool

cURL to Axios Converter

New

Convert cURL commands into an Axios request config with params, data, auth and timeouts.

Open tool