gistfile1.txt

$ kubectl create token default >token

$ awk -F. '{print $2}' token
eyJhdWQiOlsiaHR0cHM6Ly9rdWJlcm5ldGVzLmRlZmF1bHQuc3ZjLmNsdXN0ZXIubG9jYWwiXSwiZXhwIjoxNjYxMTcyMzc2LCJpYXQiOjE2NjExNjg3NzYsImlzcyI6Imh0dHBzOi8va3ViZXJuZXRlcy5kZWZhdWx0LnN2Yy5jbHVzdGVyLmxvY2FsIiwia3ViZXJuZXRlcy5pbyI6eyJuYW1lc3BhY2UiOiJkZWZhdWx0Iiwic2VydmljZWFjY291bnQiOnsibmFtZSI6ImRlZmF1bHQiLCJ1aWQiOiI3OGZkNjM0MS0yMDUyLTQ5ZjYtOWViZC1hMWY0OTEyODBiMDQifX0sIm5iZiI6MTY2MTE2ODc3Niwic3ViIjoic3lzdGVtOnNlcnZpY2VhY2NvdW50OmRlZmF1bHQ6ZGVmYXVsdCJ9

$ awk -F. '{print $2}' token | base64 -d
{"aud":["https://kubernetes.default.svc.cluster.local"],"exp":1661172376,"iat":1661168776,"iss":"https://kubernetes.default.svc.cluster.local","kubernetes.io":{"namespace":"default","serviceaccount":{"name":"default","uid":"78fd6341-2052-49f6-9ebd-a1f491280b04"}},"nbf":1661168776,"sub":"system:serviceaccount:default:default"}

$ awk -F. '{print $2}' token | base64 -d | jq -r '.exp'
1661172376

$ awk -F. '{print $2}' token | base64 -d | jq -r '.exp' | awk '{print strftime("%c",$1)}'
Mon 22 Aug 2022 09:46:16 PM JST