Regex and cron

Cron Expression for Every 12 Hours

At midnight and noon (00:00 and 12:00) every day. Copy it, check the next runs in your time zone and grab a snippet for your platform.

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Cron expression

0 */12 * * *
Customize
0minuteMinute: at minute 0 (on the hour)*/12hourHour: every 12 hours: 00:00 and 12:00*day (month)Day of month: every day of the month*monthMonth: every month*day (week)Day of week: every day of the week

At midnight and noon (00:00 and 12:00) 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 */12 * * *  /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 12 hours is 0 */12 * * *. The */12 step in the hour field keeps hours 0 and 12 from the range 0 to 23, and the 0 in the minute field runs the job on the hour, so it fires at midnight and noon every day. Shift both runs with a range, for example 0 6-23/12 * * * for 06:00 and 18:00.

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

How to use this schedule

  1. 1Copy 0 */12 * * * 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.

How does the */12 step work?

A step selects every nth value of a field, starting from the field's minimum. The hour field runs from 0 to 23, so */12 keeps 0 and 12, and nothing else fits. The sequence restarts every day: cron does not remember the previous run or count twelve hours from it. The "every 12 hours" rhythm comes entirely from the calendar.

Twelve works because it divides 24. Steps that don't divide 24 look like intervals but aren't:

ExpressionRuns atGaps
0 */12 * * *00:00, 12:0012 h, 12 h
0 6-23/12 * * *06:00, 18:0012 h, 12 h
0 */9 * * *00:00, 09:00, 18:009 h, 9 h, then 6 h
0 */16 * * *00:00, 16:0016 h, then 8 h

To move the pair, start the range at any hour from 0 to 11: 0 9-23/12 gives 09:00 and 21:00, and 30 7-23/12 gives 07:30 and 19:30.

Should I use */12 or a list of two hours?

For midnight and noon they are identical: 0 */12 * * * and 0 0,12 * * * match the same two times. The difference is intent. The step tells the next reader "evenly spaced, twelve hours apart", while a list says "these two specific times" and lets you choose uneven ones such as 08:00 and 17:00. If that is what you really need, see twice a day.

Two runs a day also means each run carries a lot of weight. If the server is down at noon, cron simply skips that run; it never catches up. Design the job to process everything since its last successful run rather than "the last 12 hours", and the occasional missed or late run stops mattering. For more frequent checkpoints, every 6 hours doubles the cadence; for once a day, see every day at midnight.

What does each field in 0 */12 * * * mean?

FieldValueAllowedMeaning
Minute00–59at minute 0 (on the hour)
Hour*/120–23every 12 hours: 00:00 and 12:00
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 midnight and noon (00:00 and 12:00) every day.

How do I adjust 0 */12 * * * to my own schedule?

Small edits to 0 */12 * * * cover most real-world needs:

ExpressionWhat it does
0 6-23/12 * * *Every 12 hours at 06:00 and 18:00
0 9-23/12 * * *Every 12 hours at 09:00 and 21:00
0 0,12 * * *The same midnight-and-noon schedule written as a list
30 */12 * * *Every 12 hours at 00:30 and 12:30
0 */12 * * 1-5Every 12 hours on weekdays only

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: Twice a day · Every 6 hours · Every day at midnight · Every day at noon

Browse all schedules in the cron schedule library.

How do I run 0 */12 * * * in crontab, GitHub Actions, Kubernetes and the cloud?

PlatformWrite it asTime zone
Linux crontab0 */12 * * *Server's time zone; CRON_TZ= in cronie
GitHub Actions- cron: "0 */12 * * *"UTC by default; add timezone: (IANA name)
Kubernetes CronJobschedule: "0 */12 * * *"Set timeZone: (1.27+)
Cloudflare Workers0 */12 * * *UTC only; numbers weekdays from 1 = Sunday, so use names
Vercel Cron Jobs0 */12 * * *UTC only; more than once a day needs Pro (Hobby: once a day)
AWS EventBridge Schedulercron(0 */12 * * ? *)Takes a time zone; legacy scheduled rules are UTC only
systemd timerOnCalendar=*-*-* 00,12:00:00Add a zone after the time, e.g. Europe/London

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

0 */12 * * *  /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 */12 * * *?

  • Steps only divide evenly when they divide the range. */12 is fine for 24 hours, but */16 or */9 leave a short gap before midnight because the count restarts every day.
  • */12 * * * * is every 12 minutes (at :00, :12, :24, :36, :48), which is a very different job from twice a day.
  • One of the two runs is usually at night for someone. If the job emails people or calls a partner API with business-hours limits, pick the phase deliberately instead of defaulting to midnight.
  • A missed run is simply skipped by cron. If the job must catch up, make it process everything since the last success, or use a systemd timer with Persistent=true.
  • 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

Yes. Both run at 00:00 and 12:00 every day. The step form signals evenly spaced runs; the list form lets you pick any two hours.
Start the hour range at 8: 0 8-23/12 * * * runs at 08:00 and 20:00. The list form 0 8,20 * * * does the same.
Not with one expression. Hour steps restart at midnight, so 0 */16 * * * runs at 00:00 and 16:00 with only 8 hours between 16:00 and midnight. For a true 16-hour interval, use a scheduler with fixed intervals, such as a systemd timer with OnUnitActiveSec=16h.
No. Cron matches clock times, so 0 */12 * * * always runs at midnight and noon regardless of when it was installed.

Last updated by the Playxoft engineering team.

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