Glossary
What is a trusted timestamp?
Trusted timestampmp is a time attached to a signature by an independent time authority. A signature alone proves who signed what, not when.
A signing device’s clock can be set to any time, so a time read from it proves nothing. A timestamp authority signs the time itself, so a third party can rely on it.
When the question is “was this signed before the deadline?”, the answer needs a trusted timestamp, not a signature alone.