Question 1

What makes a cron expression invalid?

Accepted Answer

Common causes: wrong number of fields, out-of-range values (e.g., minute 99), unsupported tokens for the dialect, or both day-of-month and day-of-week specified when one must be '?'.

Question 2

What is the difference between Unix and Quartz cron?

Accepted Answer

Unix cron has 5 fields. Quartz has 6-7 fields (adds seconds, optionally year) and requires one of day-of-month or day-of-week to be '?'.

Question 3

How to test cron without waiting?

Accepted Answer

Paste your expression into the validator, select the dialect, and see the next 5 scheduled run times instantly.

Question 4

Why does my cron work locally but fails in Kubernetes?

Accepted Answer

Kubernetes uses UTC by default. Your local cron may use a different timezone. Also, K8s does not support @shorthand notation.

Question 5

How to fix bad minute or bad hour errors?

Accepted Answer

Check that each field value is within its valid range: minute 0-59, hour 0-23, day-of-month 1-31, month 1-12, day-of-week 0-6.

Cron Validator