Back to Error DirectoryW3C EPUBCheck Standard
OPF-054Critical Ingestion Error

Date value "resource" is not valid as per http://www.w3.org/TR/NOTE...

Date value "resource" is not valid as per http://www.w3.org/TR/NOTE-datetime:resource.

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PreFlight checks for OPF-054 issues in memory and provides 1-click remediation during client-side packaging.

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What This Error Means in Plain English

EPUBCheck detected Date value "resource" is not valid as per http://www.w3.org/TR/NOTE-datetime:resource.. Digital reading systems and bookstores require standard conformance to ensure compatibility across all reading apps.

Why Retailers & EAA Regulations Block This File

Automated book distributors (Apple Books, Amazon KDP, Kobo, and IngramSpark) run strict EPUBCheck validation on ingest and reject non-compliant files.

Technical Specification: W3C EPUBCheck rule OPF-054: Date value "resource" is not valid as per http://www.w3.org/TR/NOTE-datetime:resource.

Manual Fix Instructions (for Sigil / Calibre)

  1. Locate the file and line flagged under rule OPF-054 in your EPUB editor (Sigil or Calibre).
  2. Apply the required syntax correction matching the OPF-054 specification.
  3. Re-pack and validate with PreFlight EPUB to confirm zero residual errors.