BOOKS AND JOURNALS
MAGAZINES, NEWSLETTERS, NEWSPAPERS
WEBSITES AND WEBPAGES (from the APA Style blog)
If the publication date is not clearly mentioned at the beginning of the document, look at the end (e.g. a statement that may say something like: "this document was finalized in 1990...", so that would be the date to use).
If a footer on a webpage says, “This page was last modified on [date]”, then this is NOT the date to use. It COULD be the date that the document was published, but it may also be the date when the webmaster added some code to the page.
Some sites place a copyright date for the website at the bottom of every page. Check a few pages on the site; if the identical statement appears on every page, it’s a site-wide footer, so that’s NOT the date to use. In that case, if no actual publicationdate can be found, enter (n.d.)
NO DATE AVAILABLE