Citation, Documentation of Sources
Q. I am copyediting a short report that makes reference to Wikipedia. In citing this, is it necessary to put the specific date the article was accessed, as the article may later change?
A. Yes, it’s a good idea to note the date of access for web pages that change constantly. Citations of pages that are records of a static print version, like those of many published journals, don’t necessarily require the date of access. In the case of Wikipedia, more useful than an access date is the last-modified date posted with the article. For examples, see CMOS 14.207.