In determining novelty, a prior-art document is to be read as it would have been read by a person skilled in the art on the relevant date of the document. By "relevant" date is meant the publication date in the case of a previously published document and the date of filing (or priority date, where appropriate) in the case of a document according to Art. 54(3) (see G‑IV, 5.1).
Source: http://www.epo.org/law-practice/legal-texts/html/guidelines/e/g_vi_3.htm
Date retrieved: 17 May 2021