Caveat - timestamp servers are a thing... Having your certificate cross-signed by a timestamp server ensures that even if the root certificate expires your app

Caveat - timestamp servers are a thing... Having your certificate cross-signed by a timestamp server ensures that even if the root certificate expires your application can continue to run provided that a timestamp server was in fact used at the moment of signing, and thusly vetted the certificate authority at that time. This allows for windows applications signed long before their cert expired can continue to run until a new signed version is deployed. This doesn't take into account certificate revocation. Regardless, moving the date up is a good way to test.