Also a non-redactable public record, although it's a bit hard to do that robustly; you need a transaction saying "find md5^[N]([X]) xor [md5^N(X) xor data]" to ensure you data is already securely embedded before anyone can determine that it's classified/copyrighted/otherwise-censor-bait.
It's not just related, it's the entire idea of the blockchain. It only exists to timestamp data; in the case of Bitcoin that data is a commitment to a set of transactions.