cron expression · plain english
Cron every 6 hours
Fires at 00:00, 06:00, 12:00, 18:00 — quarter-day cadence. Common for jobs that need '4 times a day' framing.
beginner
POSIX / Jenkins / Quartz / AWS
0 */6 * * *
cron every 6 hours.
Next 5 fire times
Computed live in your local timezone. The cron expression itself is timezone-agnostic — these times reflect your browser clock.
Cross-system syntax variants
Same intent, different schedulers. Use this table when migrating between systems.
| System | Expression | Note |
|---|---|---|
| Standard cron (POSIX) | 0 */6 * * * | fires at 00, 06, 12, 18 |
| Cron (verbose alt) | 0 0,6,12,18 * * * | explicit list |
| Jenkins | H H/6 * * * | H prevents :00 stampede |
| Quartz (Java) | 0 0 0/6 * * ? | 6-field, hour-step |
| systemd timer | OnCalendar=00,06,12,18:00 | explicit list form |
| AWS EventBridge | cron(0 0/6 * * ? *) | for quarter-day alignment |
Common pitfalls
- Quarter-day cadence is a daylight-affected schedule — 06:00 means local-time 06:00, which shifts under DST.
- If you have both `0 */6 * * *` and `0 12 * * *`, the noon fire happens twice. Either remove the second OR explicitly set offsets.
- On systems with frequent restarts, missed fires don't replay by default. Use `anacron` if persistence matters.
Use cases
- Polling rate-limited APIs (4 calls/day fits free tier)
- Database vacuum / analyze cycle
- Rotate ephemeral certs / tokens with 6h+ TTL
- Sync sister-region replica deltas
Translate any cron expression
cronwtf takes any cron string and returns plain-English description plus the next 5 fire times in your timezone. Standard 5-field, Jenkins H, Quartz 6-field — all supported.
Open cronwtf
Related cron schedules
cron every friday at 5 pm (end of work week) · cron on the last day of every month (quartz only) · how to run a cron job every 10 minutes · cron: every day at noon (12:00)