Date of publication vs. date of current version
Many journals offer an "early access" or "preprint" service, in which articles are made available online directly after final acceptance but before copy-editing and typesetting (i.e., before adaptation of the article to the journal's format and paper print requirements). The date of publication is the date when the article is first made available online.

After typesetting is done (which may be a few weeks later), the online version of the article is updated with the typeset version. The date of current version will be updated here, but the date of publication will still be the date when the preprint was made available.