This really is trivial, but I am determined to find the answer, if one exists! In something I recently wrote, I was advised that there is no comma after the year in a date, if the date is used as an adjective. The commenter knows this from the past but is not referencing a particular style guide. I sought to find an authoritative support for that position.
As examples, we have the following where the date is an adjective:
The September 11, 2001 attacks on the World Trade Centre…
The September 11, 2001, attacks on the World Trade Centre…
I have looked at style guides, or read references, to them (APA, MLA, Oxford) and a writer’s handbook. I have asked the question of English teachers and writers. I have, of course, searched the Web. The general findings are that the comma is called for, and there is no specific reference to when the date is an adjective.
There are three sources that give this answer, but I am looking for an authority.
1. In Wikipedia, it states, “you do not include a comma after the year where the date is serving as a specifically identifying adjective – almost as a title: ‘The September 11, 2001 attacks on the WTC brought a renewed feeling of patriotism'” (http://en.wikipedia.org/wiki/Comma). No authority is cited.
2. One online punctuation guide states, “When a date is used as an adjective, some authorities omit the comma following the year, yet others require it. Given the uncertainty, it is best to recast the sentence” (http://www.thepunctuationguide.com/comma.html). There is no identification of ‘some authorities.’
3. One more example, in a forum, a ‘veteran member’ wrote, “Here, ‘August 13, 2002’ is an adjective modifying ‘letter’, so we do not want a comma after the year.” (http://www.englishforums.com/English/CommasAndDates/wxjj/post.htm). Again, there is no authority to which we might refer.
I am certainly open to the possibility that there is a style guide that calls for no comma after a year in a full date when the date is used as an adjective. My search has not been exhaustive. I hope you might help by identifying such a guide or authority if you know of one!