Question 1

How many fields does a cron expression have?

Accepted Answer

POSIX cron uses 5 fields: minute, hour, day-of-month, month, day-of-week. Quartz adds seconds (6) or seconds + year (7). AWS EventBridge is 6-field with a year. This tool targets the most common POSIX 5-field form.

Question 2

Does 1-5 in 0 9 * * 1-5 mean Monday through Friday?

Accepted Answer

Yes. The weekday field maps 0=Sun, 1=Mon, …, 6=Sat, 7=Sun (alias). So 1-5 is Monday–Friday. Implementations agree that both 0 and 7 represent Sunday.

Question 3

Is */5 * * * * really "every 5 minutes"?

Accepted Answer

Yes, but it fires on minutes 0, 5, 10, …, 55 — aligned to the hour, not "every 5 minutes starting from when the service booted".

Question 4

How is the expression interpreted when both day-of-month and day-of-week are set?

Accepted Answer

POSIX and Vixie cron OR the two fields — fire when either matches. Quartz ANDs them and requires ? in one of them. This tool uses POSIX OR. Example: 0 0 13 * 5 fires on the 13th OR any Friday — it is not "Friday the 13th".

Question 5

Do shortcuts like @daily and @hourly work?

Accepted Answer

Yes — @yearly, @monthly, @weekly, @daily/@midnight and @hourly are all recognised and expanded to their 5-field equivalents.

Question 6

Which timezone are the "next runs" in?

Accepted Answer

All next-run times use Korea Standard Time (KST, UTC+9). Subtract 9 hours for the equivalent UTC time if your production scheduler runs in UTC.

Question 7

Can I use this translator for GitHub Actions schedule:?

Accepted Answer

Yes — GitHub Actions accepts POSIX 5-field. But it always runs in UTC, so shift your expression by 9 hours for KST. 9 AM KST becomes 0 0 * * * (midnight UTC).

Question 8

Does the output work in Kubernetes CronJob?

Accepted Answer

Yes — spec.schedule is POSIX 5-field. Set spec.timeZone: "Asia/Seoul" (Kubernetes 1.27+) for KST, or rewrite the expression for UTC on older versions.

Question 9

Is AWS EventBridge cron the same syntax?

Accepted Answer

No — EventBridge uses 6 fields (minute, hour, day, month, weekday, year) and supports ?, L, W, #. A POSIX 5-field expression will fail. An EventBridge-specific tab is planned.

Question 10

Is my cron expression sent to a server?

Accepted Answer

No. Parsing and next-run calculation run entirely in your browser in JavaScript. Once the page is loaded you can disconnect the network and the tool keeps working. The expression never leaves your device.

Question 11

Which phrases does the natural-language → cron feature recognise?

Accepted Answer

The current patterns are Korean-leaning: "매 분", "매 N분마다", "매일 오전 9시", "평일 오후 6시 30분", "매주 월요일 자정", "매월 1일 자정", "매년 1월 1일 자정", weekday ranges, etc. English coverage is limited for now.

Question 12

How is this different from crontab.guru?

Accepted Answer

crontab.guru is English-only. This tool leads with a Korean description (English alongside), shows the next 10 runs in KST, adds Korean natural-language-to-cron reverse conversion, and ships 20 presets aligned with Korean teams. Quartz extensions (L, W, #) are not yet supported here.

Question 13

I need second-level cron.

Accepted Answer

Sub-minute cron exists only in 6-field dialects (Quartz, Jenkins, some Kubernetes wrappers). POSIX cron is minute-level minimum. Use an application-level scheduler (Spring @Scheduled, APScheduler) or Quartz. A Quartz tab is on our roadmap.

Question 14

What if I specify a non-existent date like Feb 30?

Accepted Answer

The expression parses but will never fire. If the next-runs list is empty, check for this. For "last day of February" you need Quartz L, which this tool does not yet support.

Question 15

Is it open source?

Accepted Answer

Not public yet, but the entire parsing / describing / next-runs / reverse logic lives in a single src/lib/cronParser.ts using nothing but standard browser APIs. Open-sourcing is under consideration.

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