Why does timezone matter for cron?

A cron expression like `0 9 * * 1-5` means '9 AM on weekdays' — but in WHICH timezone? Most servers default to UTC, but most humans think in their local time. A 9 AM ET cron job hits at 13:00 or 14:00 UTC depending on DST. This tool makes the timezone explicit so you can predict actual fire times.

Which cron syntax is supported?

Standard 5-field syntax: minute (0-59) hour (0-23) day-of-month (1-31) month (1-12) day-of-week (0-6, 0=Sunday). Each field supports `*`, lists `1,5,15`, ranges `1-5`, steps `*/15`, and combinations like `1-30/2`. Aliases like `@daily` or special seconds-fields (Quartz/AWS 6-7 fields) are not supported.

How are day-of-month and day-of-week combined?

POSIX cron OR-combines them: `0 0 1 * 1` fires on the 1st AND every Monday. If only one of the two is restricted (the other is `*`), only the restricted one matters. This implementation follows POSIX behavior.

What about DST transitions?

The next-fire algorithm steps minute-by-minute and re-formats each candidate in the target timezone, so DST transitions are handled correctly — fires that fall in the 'lost hour' on spring-forward day are skipped, and fires in the 'gained hour' on fall-back day fire at the first occurrence only (matching most cron implementations).

What's the IANA timezone format?

Continent/City format like `America/New_York`, `Europe/London`, `Asia/Seoul`, `Australia/Sydney`. Abbreviations like 'EST' or 'PDT' are NOT IANA-compliant because they don't account for DST — always use the full Continent/City name. The dropdown shows common ones.

Cron with Timezone

Developer Tools· 34 tools

Free timezone-aware cron evaluator. Type a 5-field cron expression (minute hour day month weekday), pick the IANA timezone the schedule runs in, and see the next 5 fire times in that timezone — plus how long from now each one is. Built for engineers debugging cron jobs that run on a server in a different timezone than the user.

Cron expression

Fields: minute hour day-of-month month day-of-week

Presets

Timezone

Field syntax · `*`, `1,5,15`, `1-5`, `*/15`, `1-30/2`

POSIX OR rule · day-of-month and day-of-week combine with OR if both restricted

Description

Fires at minute 0 of hour 9 every month on Mon,Tue,Wed,Thu,Fri.

Next 5 fire times in America/New_York

Tue, Jun 23, 2026, 09:00 EDTin 15h 17m
Wed, Jun 24, 2026, 09:00 EDTin 2d 15h
Thu, Jun 25, 2026, 09:00 EDTin 3d 15h
Fri, Jun 26, 2026, 09:00 EDTin 4d 15h
Mon, Jun 29, 2026, 09:00 EDTin 7d 15h

Frequently Asked Questions

References

POSIX crontab specification — The Open Group
IANA Time Zone Database — IANA

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Frequently Asked Questions

References and sources

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