Quartz to cron

Quartz + AWS cron() · L W # guards · checked run by run

Paste a Quartz expression (or an AWS EventBridge cron(…)) and get crontab lines for Linux. What cron can say is translated directly; what it cannot — last day, nearest weekday, nth weekday — becomes a line that runs on every candidate day with a date test in front of the command, and the combination is checked against the original over the next 300 runs.

Quartz or AWS expression

Source Command Keep the year as a date test

Unix cron

Try one

How to convert Quartz to cron

Paste the Quartz expression, six or seven fields starting with seconds. An AWS cron(…) switches the source to AWS by itself (AWS has no seconds field and requires the year).
Put your command in the Command box so the crontab lines come out complete.
Copy the crontab block. Guarded lines are normal crontab lines: the schedule picks every day that could match, and the test before && lets the command run only on the right one.
Check the green line — the lines (with their date tests applied) produce the same runs as the Quartz expression.
If the expression has a year, decide: the year is dropped by default (with a warning), or tick Keep the year to add a date +%Y test.

Guards for what cron cannot say

Unix cron accepts numbers, names, *, ,, - and / — no L, W or #. Each of those becomes a range of candidate days plus a test with GNU date:

Quartz	Means	Cron days	Test before the command
L	last day of the month	28-31	[ "$(date -d tomorrow +\%d)" = 01 ]
L-3	3 days before the last day	25-28	[ "$(date -d '+4 days' +\%d)" = 01 ]
2#1	first Monday	1-7	[ "$(date +\%u)" = 1 ]
6#3	third Friday	15-21	[ "$(date +\%u)" = 5 ]
6L	last Friday	22-31	[ "$(date +\%u)" = 5 ] && [ "$(date -d '+7 days' +\%m)" != "$(date +\%m)" ]
LW	last weekday	28-31 and 26-31	two lines: the last day when it is Mon–Thu; a Friday whose next Monday is in the next month
15W	weekday nearest the 15th	14, 15, 16	three lines: the 15th on a weekday, Friday the 14th, Monday the 16th

The first-Monday line works because the day-of-week field stays *. Writing 0 12 1-7 * 1 instead is a well-known trap: with both day fields set, Linux cron runs when either matches, so that line fires on the 1st to the 7th and on every Monday.

Two details that break guards

Escape every %. In a crontab, a bare % in the command becomes a newline and everything after it is fed to the command as standard input. The lines above use \%, and a % in your own command is escaped for you.
date -d is GNU date. It is the default on Linux. BSD and macOS date spell "tomorrow" as date -v+1d; on a Mac, the launchd converter is usually the better route.

FAQ

What happens to the seconds field?

Cron has one-minute resolution. A seconds value of 0 simply disappears. Anything else cannot be expressed: for up to four second values the page writes one line per value with sleep N && in front of the command (close, not exact), and says so; more than that is refused.

Does it handle AWS EventBridge expressions?

Yes. AWS cron(minutes hours day-of-month month day-of-week year) numbers the week 1-7 with 1 = Sunday, like Quartz, and uses the same L, W and #. EventBridge rules run in UTC, so the crontab should run on a UTC clock too (or under CRON_TZ=UTC with cronie).

Why is the year dropped?

Unix cron has no year field. Dropping it means the job runs every year, so the page warns you. If the year is a single value or one range, tick "Keep the year" to test it in the command instead.

Why not just run the job daily and check the date in the script?

You can — the guard is exactly that check, moved into the crontab line. Narrowing the schedule to the candidate days (28-31 for "last day") means cron starts the job four times a month instead of thirty.