Unixcop shows you how to remove an expired key in APT.

Remove an expired key in APT

lthough it is not always recommended, many times to get recent versions of a package or a whole program, we need to add external repositories. Usually, these repositories have a GPG key that allows us to secure the installation. What happens when these GPG keys expire? 

Remove an expired key in APT - Unixcop the Unix / Linux the admins deams