Kubernetes CronJob validator

Why kubectl get cronjob lies about next run

The NEXT SCHEDULE column is a convenience view, not a contract. It can hide the controller manager timezone, miss a deprecated CRON_TZ prefix, and gives you no sense of what happens across daylight-saving transitions. A CronJob that looks clean in UTC can behave differently once spec.timeZone is set to a regional IANA zone.

DST in K8s - the 5-minute version

Kubernetes evaluates CronJobs against the schedule timezone. When clocks spring forward, wall-clock times inside the missing hour do not exist and the run is skipped. When clocks fall back, the same wall-clock time can occur twice. For generic cron exploration, use the cron visualizer.

concurrencyPolicy in plain English

Allow starts every scheduled job even if the previous one is still running. Forbid skips the new run while an older job is active. Replace terminates the active job and starts the new one. startingDeadlineSeconds controls how far Kubernetes will look back for missed runs after downtime before dropping them.