Cron expression `10 15 21 DEC 0,6` runs at 15:10, on day 21 of the month, and on Sunday and Saturday, only in December

Read more in the dedicated guide: Cron weekends.

What this cron means, field by field

Each field of 10 15 21 DEC 0,6 controls one dimension of the schedule. Hover over any value in the editor above to see its tooltip; the table below summarises the same information.

Field	Value	Means	Range / hint
minute	`10`	at minute 10	0-59. The minute(s) of the hour the job will fire.
hour	`15`	at hour 15	0-23. The hour(s) of the day the job will fire (0 = midnight, 23 = 11 PM).
day of month	`21`	at day of month 21	1-31. The day(s) of the month. Use * if you want every day.
month	`DEC`	at month DEC	1-12 or JAN-DEC. The month(s). Use * for every month.
day of week	`0,6`	at day of week 0, 6	0-7 or SUN-SAT (0 and 7 both mean Sunday). Use * for every day of the week.

Next 5 runs

Shown in UTC. Change the timezone in the editor.

Next runs · UTC

Sat 5 Dec · 15:10in 79d 22h
Sun 6 Dec · 15:10
Sat 12 Dec · 15:10
Sun 13 Dec · 15:10
Sat 19 Dec · 15:10

Where else this cron could be used

The same expression 10 15 21 DEC 0,6 works in:

Standard Unix crontab (5-field syntax).
AWS EventBridge / Lambda Scheduled (with a 6th field for year, often *).
Vercel cron jobs (declared in vercel.json).
Quartz Scheduler and node-cron, robfig/cron and similar libraries.

Examples

0 18 * * *
Every day at 18:00
0 */5 * * *
Every 5 hours
0 18 * * 1-5
Weekdays at 18:00
0 0 1 * *
Once a month, on the 1st at midnight

Cheatsheet

Full cheatsheet

Field	Req.	Range	Wildcards
minute	yes	0-59	, - * /
hour	yes	0-23	, - * /
day of month	yes	1-31	, - * /
month	yes	1-12 or JAN-DEC	, - * /
day of week	yes	0-6 or names; some dialects use 0-7 or 1-7 — see Dialects	, - * /

Frequently asked questions

What does the cron expression `10 15 21 DEC 0,6` mean?

at 15:10, on day 21 of the month, and on Sunday and Saturday, only in December.

When does `10 15 21 DEC 0,6` run next?

The next runs (UTC): 2026-12-05 15:10; 2026-12-06 15:10; 2026-12-12 15:10; 2026-12-13 15:10; 2026-12-19 15:10.

Is `10 15 21 DEC 0,6` a valid cron expression?

Yes - CronTool's parser accepts this expression and the calendar projects future runs successfully.

What this cron means, field by field

Next 5 runs

Where else this cron could be used

Frequently asked questions

Stop pasting `10 15 21 DEC 0,6` into a host you also have to babysit.