Question 1

What is a cron expression?

Accepted Answer

A cron expression is a compact schedule string of five space-separated fields: minute, hour, day of month, month, and day of week. For example, "0 14 * * 1" means "at 14:00 every Monday". Schedulers like crontab, Kubernetes CronJobs, and Quartz read these fields to decide when a job runs.

Question 2

How do I read the five fields of a cron expression?

Accepted Answer

Read them left to right: minute (0-59), hour (0-23), day of month (1-31), month (1-12), day of week (0-7, where both 0 and 7 mean Sunday). An asterisk means "every value", a hyphen gives a range (1-5), a slash gives a step (*/10 = every 10), and commas list values (1,15,30).

Question 3

Why does my cron job with both day-of-month and day-of-week restricted behave unexpectedly?

Accepted Answer

In standard Vixie cron, when BOTH the day-of-month and day-of-week fields are restricted (not *), the job runs when EITHER matches — a union, not an intersection. So "0 0 1 * 1" fires on the 1st of the month AND every Monday. If you need an AND, you need a scheduler with that semantics (like Quartz with the ? placeholder) or extra logic in your script.

Question 4

What is the difference between 0 9 * * 1-5 and 0 9 * * MON-FRI?

Accepted Answer

Nothing — they are identical. Cron accepts English three-letter names (MON-FRI, JAN-DEC) as alternatives to numbers in the weekday and month fields. Names are case-insensitive. CronVibe translates both forms to the same schedule and shows the plain-English meaning.

Question 5

How does CronVibe predict future execution times?

Accepted Answer

After parsing your expression into five field masks, CronVibe walks forward minute by minute from the next minute after now, skipping ahead intelligently (whole months, whole days, whole hours) when a field doesn't match, and collects the next five timestamps the expression would fire. It uses your local time zone, just like a system crontab would.

Question 6

Does CronVibe support @daily, @hourly, and other cron shortcuts?

Accepted Answer

Yes. The @yearly, @annually, @monthly, @weekly, @daily, @midnight, and @hourly aliases are expanded to their full five-field forms before parsing, and the expansion is shown so you always know exactly what runs.

Field	Allowed values	Special characters
`minute`	0–59	, - * /
`hour`	0–23	, - * /
`day of month`	1–31	, - * / ? (L W in Quartz)
`month`	1–12 or JAN–DEC	, - * /
`day of week`	0–7 or SUN–SAT (0 and 7 = Sunday)	, - * /

`*`	every value of the field
`5`	exactly this value
`1-5`	range: 1 through 5
`*/10`	step: every 10th value
`0,30`	list: both 0 and 30
`9-17/2`	range with step: 9, 11, 13, 15, 17

`0 9 * * 1-5`	weekdays at 09:00
`/15 * * *`	every 15 minutes
`0 2 * * 6`	Saturdays at 02:00
`0 0 1 * *`	first of every month
`30 4 1,15 * *`	1st and 15th at 04:30
`0 22 * * 1-5`	weekdays at 22:00

Cron Expression Generator & Explainer

Cron Field Cheat Sheet

AOperators in one glance

BEveryday examples

CThe day-of-month / day-of-week trap