# EPUBCheck OPF-054: invalid metadata date, how to fix it

Source: https://epubcc.com/epubcheck/opf-054/ (updated 2026-11-04)

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. EPUBCheck quotes the value and the reason, and an invalid date is an error rather than a style warning.

- Official message (EPUBCheck 5.4.0): Date value "%1$s" is not valid as per http://www.w3.org/TR/NOTE-datetime:%2$s.
- Default severity: Error

## Typical causes

- Impossible dates such as 2020-13-01 or 2021-02-30.
- Text that is not a date in a date field, such as "unknown" or "n/a".
- Day and month swapped in an imported value.

## How to fix it

1. Find the date element EPUBCheck points to.
2. Correct the value to a real date in YYYY, YYYY-MM or YYYY-MM-DD form.
3. If the date is unknown, remove the element instead of filling it with placeholder text.

## When it's not this

If the date is real but written in another format, that is OPF-053, a warning.

## Sources

- EPUB 3.3, §5.5.3.2.4 The dc:date element: https://www.w3.org/TR/epub-33/#sec-opf-dcdate (read 2026-11-04)

Message text and severity: EPUBCheck (W3C, BSD-3-Clause). Explanation: EpubCC.