GL G IV 7.5.4 Disclosures which have no date or an unreliable date

Where an internet disclosure is relevant for examination but does not give any explicit indication of the publication date in the text of the disclosure, or if an applicant has shown that a given date is unreliable, the examiner may try to obtain further evidence to establish or confirm the publication date. Specifically, the examiner may consider using the following information:
(a)Information relating to a web page available from an internet archiving service. The most prominent such service is the Internet Archive accessible through the so-called "Wayback Machine" ( The fact that the Internet Archive is incomplete does not detract from the credibility of the data it does archive. It is also noted that legal disclaimers relating to the accuracy of any supplied information are routinely used on websites (even respected sources of information such as Espacenet or IEEE), and these disclaimers are not to be taken to reflect negatively on the websites' actual accuracy.
(b)Timestamp information relating to the history of modifications applied to a file or web page (for example, as available for wiki pages such as Wikipedia and in version control systems as used for distributed software development). 
(c)Computer-generated timestamp information as available from file directories or other repositories, or as automatically appended to content (e.g. forum messages and blogs). 
(d)Indexing dates given to the web page by search engines (see also T 1961/13). These will be later than the actual publication date of the disclosure, since the search engines take some time to index a new website.
(e)Information relating to the publication date embedded in the internet disclosure itself. Date information is sometimes hidden in the programming used to create the website but is not visible in the web page as it appears in the browser. Examiners may, for example, consider the use of computer forensic tools to retrieve such dates. In order to allow a fair evaluation of the accuracy of the date by both the applicant and the examiner, these dates can be used only if the examiner knows how they were obtained and can communicate this to the applicant. 
(f)Information about replication of the disclosure at several sites (mirror sites) or in several versions. 
It may also be possible to make enquiries with the owner or the author of the website when trying to establish the publication date to a sufficient degree of certainty. The probative value of statements so obtained will have to be assessed separately.
If no date can be obtained (other than the date of retrieval by the examiner, which will be too late for the application in question), the disclosure cannot be used as prior art during examination. If a publication, although undated, is highly relevant to the invention and can therefore be considered to be of interest to the applicant or third parties, it may be cited in the search report as an "L" document. The search report and the written opinion must explain why this document was cited. Citing the disclosure will also make it citable against future applications, using the date of retrieval as the date of publication.

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EPO Guidelines - B Search

EPO Guidelines - G Patentability

General Case Law