Question 1

What is a cron expression?

Accepted Answer

A cron expression is a 5- or 6-field string that describes a recurring schedule. The fields are minute, hour, day of month, month, and day of week, optionally preceded by a seconds field. Linux crontab, systemd timers, and Kubernetes CronJobs all use this syntax.

Question 2

What is the difference between 5-field and 6-field cron?

Accepted Answer

Standard cron uses 5 fields (minute hour day-of-month month day-of-week). Some schedulers, such as Quartz and Spring, add a leading seconds field for 6-field expressions. This tool parses both and shows a seconds row when a 6-field expression is detected.

Question 3

What do L, W, and # mean in a cron expression?

Accepted Answer

L, W, and # are non-standard Quartz extensions. L means last day of the month or last weekday, W means the nearest weekday to a given day, and # means the nth occurrence of a weekday in a month, such as 1#2 for the second Monday. The tool displays them and explains them, but the preview of next runs is unavailable for expressions that use them.

Question 4

How do I write every Monday through Friday at 9am?

Accepted Answer

Use 0 9 * * 1-5, or select the Weekdays at 09:00 preset. Day-of-week numbers run from 0 (Sunday) to 6 (Saturday), and 7 is also accepted as Sunday. Names such as MON-FRI are equivalent to 1-5.

Question 5

How does this tool calculate the next runs?

Accepted Answer

The tool evaluates the expression against the local calendar starting from now and collects the first 5 matching moments. Each run is shown in your local time and in UTC, sorted from nearest to furthest, so you can verify the schedule before deploying it.

Question 6

What is the @reboot macro?

Accepted Answer

@reboot is a special macro that runs a command once, when the cron daemon starts or the system boots. It does not follow a recurring time pattern, so next-run preview is unavailable for it.

Question 7

Does the tool support macros like @daily and @hourly?

Accepted Answer

Yes. @yearly, @monthly, @weekly, @daily, @hourly, and @reboot are all recognized. Pasting a macro shows its explanation and highlights the equivalent preset, and you can expand it into regular fields at any time.

Question 8

Which timezone do the next runs use?

Accepted Answer

Every run is displayed twice: once in your local timezone and once in UTC. The cron expression itself has no timezone, so the same expression fires at different absolute moments for servers in different timezones. Always compare both columns when debugging a schedule.

#	Local Time	UTC	Relative
1	2026-10-06T22:33:00	2026-10-07T01:33:00.000Z	in 1 minutes
2	2026-10-06T22:34:00	2026-10-07T01:34:00.000Z	in 2 minutes
3	2026-10-06T22:35:00	2026-10-07T01:35:00.000Z	in 3 minutes
4	2026-10-06T22:36:00	2026-10-07T01:36:00.000Z	in 4 minutes
5	2026-10-06T22:37:00	2026-10-07T01:37:00.000Z	in 5 minutes

Cron Expression Builder - Visual Cron Generator & Plain-Language Explainer | ZweiDeveloper Tools

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