Sellat proof of existence for one SHA-256: anchored on Polygon in the next fast batch (minutes) and attested on Bitcoin through OpenTimestamps; certificate, proof.json and evidence ZIP, verifiable without Sellat.
eIDAS qualified electronic timestamp (RFC 3161) from an EU qualified trust service provider, on a Sellat proof of yours. Use when the date must hold before an EU court or authority: it carries the legal presumption of accuracy of art. 41.2 eIDAS. Issued in seconds.