OPF-054 is reported as error by default. The EPUB breaks a rule of the specification and is invalid. Stores and Send to Kindle may reject it, and EPUBCheck exits with status 1.

EPUBCheck · Package document (OPF)

`OPF-054`

Updated: Nov 3, 2026

EPUBCheck OPF-054 is an error message: “Date value "…" is not valid as per http://www.w3.org/TR/NOTE-datetime:….” A date in the metadata is not a valid date.

The official message

Date value "%1$s" is not valid as per http://www.w3.org/TR/NOTE-datetime:%2$s.

Default severity: Error. The EPUB breaks a rule of the specification and is invalid. Stores and Send to Kindle may reject it, and EPUBCheck exits with status 1.
EPUBCheck version: 5.4.0

%1$s, %2$s… are filled in with the file, value or element EPUBCheck found.

Typical causes

Impossible dates such as 2020-13-01, or text that is not a date in a date field.

How to fix it

Correct the value to a real date in YYYY, YYYY-MM or YYYY-MM-DD form.

Terms used here

Other OPF messages

OPF-053 Date value "…" does not follow recommended syntax as per http://www.w3.org/TR/NOTE-datetime:….
OPF-050 TOC attribute references resource with non-NCX mime type; "application/x-dtbncx+xml" is expected.
OPF-049 Item id "…" was not found in the manifest.
OPF-048 Package tag is missing its required unique-identifier attribute and value.
OPF-060 Duplicate entry in the ZIP file: "…" (file names must be unique after Unicode canonical normalization and full case folding).
OPF-062 Found Adobe page-map attribute on spine element in opf file.

Message text and severity from EPUBCheck 5.4.0 (W3C, BSD-3-Clause). Explanation by EPUBLab.