I have used kubectl get pods -n somenamespace but it gives the AGE and not how much time has passed after the pod has gone to terminating state.
Thanks in advance
You have to get the pod name using the following command
$ kubectl get pods -n somenamespace | grep Terminating
some-pod-7c5d849f6b-qv48m 1/1 Terminating 0 17h
Then you can run the following command to get what you need
$ kubectl describe pod some-pod-7c5d849f6b-qv48m -n somenamespace | grep Terminating
Status: Terminating (lasts 3h10m)