Unverified signed commit (expired) but locally verified

Hello everyone,

I am using a gpg key I added in 2017 to sign my commits and never had problems until now. I update the expiry date locally to keep it up-to-date.

I realised today that my commits are suddenly marked as unverified with the given reason that the key is expired.
On my machine the key is still valid until January 2021 (I always add a month) and git says the commits are signed correctly.

Does anybody have an idea what could cause this problem?
To see a repository where it happens you can check here:

I figured it out.
By looking up again how the change of expiration works in the documentation.

What confused me was that this never happened before.
When I initially uploaded the key I was not in the habit of changing the expiration monthly and I guess the default expiration ended now, so that I never encountered the need to upload the new key.

The solution was to delete the key and upload it again with the correct expiration.