Over the last decade or more, what used to be the standard manner of referring to events in the past by designating their dates in a prepositional phrase is being replaced by a hypertrophic form whereby the word back is inserted before the preposition regardless of the proximity of the past event to the speech event. Here are some recent examples:
(1) “There was a moment back in 2002 when . . . [opening sentence]” (Caryn James, “Aniston Agonistes: Good Girl, Bad Choices,” The New York Times [all references to the National Edition], 6/5/06, p. B1);
(2) “The author of seven other books, she was a fellow at the library when she first got the idea back in 2001, on 9/11″ (Patricia Cohen, NYT, 2/14/08, p. B9);
(3) “back in January” – said in February (unidentified man, viva voce; cf. [way] back [when]).
One hears such examples constantly on the radio and from ordinary speakers; moreover, the preposition in question can be on or during as well as in (back on Thursday, back during the war). And whereas the appearance of back was formerly conditioned strictly by the remoteness of the past event relative to the speech event––a form of emphasis––now the emphatic meaning is apparently being neutralized: the appearance of back is becoming de rigueur regardless of the degree of proximity of the past event (Cf. the now-common usurpation of yes as a simple affirmative by the previously emphatic absolutely).
How to explain this development? Some more or less speculative explanations come to mind.
First, there seems to be a general tendency in present-day American English in particular toward grammatical hypertrophy of all kinds, i.e., pleonastic formations that have mushroomed during the past several decades.  Among these the most relevant to the insertion of back are constructions with the deictic adverbs (out) there/here, e. g.:
(4) “There are rarely purely ideological movements out there.” (Barack Obama, quoted by David Brooks, “Obama Admires Bush,” NYT, 5/16/08, p. A23)
(5) “There’s a real world out here where people are offered . . .” (Ruth Lewin Sime, letter to the editor, NYT, 6/5/06, p. A22);
(6) “There’s a lot of sadness here.” ([in a context where the place has already been stipulated] attributed to Jamie Dettmer, director of media relations, Cato Institute, in “Columnist Resigns His Post, Admitting Lobbyist Paid Him,” NYT, 12/17/05, p. A15).
These examples can be compared to the otiose colloquial use of at after where and what, as in:
(7) “Where’s your heart rate at?” (female fitness trainer [with a B.A.], viva voce [speaking to a client wearing a monitor], W. LA, 6/5/06); cf. “What’s your heart rate at?”
They are of a piece with the occurrence of the prepositional phrase in place after the verbs be and have.
Returning now to the habitual but redundant use of the locative adverb back with designators of time, I would like to suggest a motivation that might be labeled the avoidance of placeless existence. A past event is by definition no longer existent in the same sense as a present event. This fundamental “non-is-ness” of a past event makes its designation unstable, and thereby in need of extra temporal determination. The most routine way in which all languages fix or anchor time expressions, with their quintessential instability, is by localizing them through the use of words denoting space. Accordingly, the near-obligatory extension of the emphatic word back before prepositional phrases as a designator of remoteness in time to non-emphatic contexts in contemporary speech may be yet another example of what is clearly a general grammatical tendency.