- Kubelet: Added kubelet serving certificate metric `server_rotation_seconds` which is a histogram reporting the age of a just rotated serving certificate in seconds. ([#84534](https://github.com/kubernetes/kubernetes/pull/84534), [@sambdavidson](https://github.com/sambdavidson))

  <unknown>   Normal   Scheduled           pod/nginx-6c975b59f8-gvmjr    Successfully assigned default/nginx-6c975b59f8-gvmjr to minikube
  
  $ kubectl describe pod xxx
  ......
  Events:
    Type    Reason     Age        From               Message
    ----    ------     ----       ----               -------
    Normal  Scheduled  <unknown>  default-scheduler  Successfully assigned default/nginx-6c975b59f8-gvmjr to minikube
  ......

- Added `ImageMaximumGCAge` field to Kubelet configuration, which allows a user to set the maximum age an image is unused before it's garbage collected. ([#121275](https://github.com/kubernetes/kubernetes/pull/121275), [@haircommander](https://github.com/haircommander))

- Added a "reason" field to the "image_garbage_collected_total" metric, allowing administrators to differentiate between images that were collected for reasons "age" vs "space".
   ([#123345](https://github.com/kubernetes/kubernetes/pull/123345), [@haircommander](https://github.com/haircommander))

- Change `kubectl diff --invalid-arg` status code from 1 to 2 to match docs ([#105445](https://github.com/kubernetes/kubernetes/pull/105445), [@ardaguclu](https://github.com/ardaguclu))
- Changed kubectl describe to compute age of an event using the `EventSeries.count` and `EventSeries.lastObservedTime`. ([#104482](https://github.com/kubernetes/kubernetes/pull/104482), [@harjas27](https://github.com/harjas27))

    * $ kubectl get pv --show-labels
    * NAME           CAPACITY   ACCESSMODES   STATUS    CLAIM            REASON    AGE       LABELS
    * pv-abc                5Gi        RWO                   Bound     default/claim1                    46s       failure-domain.beta.kubernetes.io/region=VC1,failure-domain.beta.kubernetes.io/zone=cluster-1

- Kubectl: Fixed panic when describing an ingress backend without an API Group ([#100505](https://github.com/kubernetes/kubernetes/pull/100505), [@lauchokyip](https://github.com/lauchokyip)) [SIG CLI]
- Kubectl: fix case of age column in describe node (#96963, @bl-ue) ([#96963](https://github.com/kubernetes/kubernetes/pull/96963), [@bl-ue](https://github.com/bl-ue)) [SIG CLI]