Verifiable Credentials issued by DIDs provide powerful verifiability on the claims made. You can trustlessly verify that a specific identity made a specific claim. But, by default, you cannot be sure *when* a claim was made. Although credentials include a `validFrom` (in the VC 2.0 spec) property indicating when the credential was issued, this is simply a claim being made by the issuer. If the issuer is a known and trusted entity, this might be alright. But in more complex systems with many p...