Many sources other than scientific publishers are generally deemed to provide reliable publication dates. These include for example publishers of newspapers or periodicals, or television or radio stations. Academic institutions (such as academic societies or universities), international organisations (such as the European Space Agency ESA), public organisations (such as ministries or public research agencies) or standardisation bodies also typically fall into this category.
Some universities host so-called eprint archives to which authors submit reports on research results in electronic form before they are submitted or accepted for publication by a conference or journal. In fact, some of these reports are never published anywhere else. The most prominent such archive is known as arXiv.org (www.arxiv.org, hosted by the Cornell University Library), but several others exist, e.g. the Cryptology eprint archive (eprint.iacr.org, hosted by the International Association for Cryptology Research). Some such archives crawl the internet to automatically retrieve publications which are publicly available from researchers' web pages, such as Citeseer or ChemXseer (citeseer.ist.psu.edu and chemxseer.ist.psu.edu, both hosted by Pennsylvania State University).
Companies, organisations or individuals use the internet to publish documents that had previously been published on paper. These include manuals for software products such as video games, handbooks for products such as mobile phones, product catalogues or price lists and white papers on products or product families. Evidently, most of these documents address the public - e.g. actual or potential customers - and are thus meant for publication. Hence the date given can be taken as a date of publication.