epub validator error, OPS/content.opf, -datetime:2019-2020 class java.lang.IllegalArgumentException MONTH.

Scrivener Scrivener for macOS
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WARNING OPS/content.opf 12 37 Date value ‘2019-2020’ does not follow recommended syntax as per w3.org/TR/NOTE-datetime:2019-2020 class java.lang.IllegalArgumentException MONTH.

I have only the copywriter 2020 in the text and no other dates.