Cron expression `*/30 16 31 JUN 1-5` runs every 30 minutes, between 16:00 and 16:59, on day 31 of the month, Monday through Friday, only in June

Read more in the dedicated guide: Cron every 30 minutes.

What this cron means, field by field

Each field of */30 16 31 JUN 1-5 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	`*/30`	every 30 minutes	0-59. The minute(s) of the hour the job will fire.
hour	`16`	at hour 16	0-23. The hour(s) of the day the job will fire (0 = midnight, 23 = 11 PM).
day of month	`31`	at day of month 31	1-31. The day(s) of the month. Use * if you want every day.
month	`JUN`	at month JUN	1-12 or JAN-DEC. The month(s). Use * for every month.
day of week	`1-5`	from day of week 1 through 5	0-7 or SUN-SAT (0 and 7 both mean Sunday). Use * for every day of the week.

Next 5 runs

This expression never fires — day 31 does not exist in June. Every field is valid on its own, but no calendar date satisfies all of them at once.

Similar cron expressions

Common variations and tweaks of */30 16 31 JUN 1-5.

Where else this cron could be used

The same expression */30 16 31 JUN 1-5 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 `*/30 16 31 JUN 1-5` mean?

every 30 minutes, between 16:00 and 16:59, on day 31 of the month, Monday through Friday, only in June.

When does `*/30 16 31 JUN 1-5` run next?

Never — day 31 does not exist in June. The expression is syntactically valid but no calendar date satisfies every field.

Is `*/30 16 31 JUN 1-5` a valid cron expression?

It parses, but it never fires: day 31 does not exist in June. Pick a day that exists in every listed month.

What this cron means, field by field

Next 5 runs

Similar cron expressions

Where else this cron could be used

Frequently asked questions

Stop pasting `*/30 16 31 JUN 1-5` into a host you also have to babysit.