According to the APA manual, writers should only include full dates in citations and references for three kinds of sources: personal communication, daily or weekly periodicals and Web-based sources with frequent dated posts, like blogs. While APA has strict guidelines for formatting date entries, the rules are straightforward and apply universally to every source regardless of its medium.
Dates in References
In a bibliographic reference, include the date entry after the author's name, before the title of the work. Make an open parenthesis. Type the year followed by a comma and a space. Spell out the month, add a space and then enter the day. Add a close parenthesis and period to conclude the date portion of the entry. For example:
Armstrong, N. (1969, July 29). [include the rest of the citation here].
Dates in In-Text Citations
APA in-text citations should only include the year of publication, even if you include the full date in the bibliographic entry. However, there is one exception to this rule: an in-text citation for unpublished personal correspondence. Enter the date at the end of the parenthetical citation. Insert a comma after the phrase “personal communication” and leave a space. Spell out the month and leave another space. Type the day followed by a comma and a space. Enter the year. Conclude the citation with a close parenthesis. For example:
(N. Armstrong, personal communication, July 29, 1969).