I'm reading an article titled "A Corpus Analysis of (The) Last/Next+ Temporal Nouns" in the Journal of English Linguistics by Isaiah WonHo Yoo, and he writes that in constructions like "last year" the addition of the definite article shifts the focus, or the initial point in time coordinates, in this way:
(The year is 2013 and a person is speaking of his friend's earlier statement:)
He said in 2003 we will travel abroad together next year. (meaning, in
Putting in THE shifts the focus to the person in the phrase:
He said in 2003 we will travel abroad together the next year.
(meaning, in 2004)
FumbleFingers mentioned this aspect in his comments at this page.
Maybe this THE-induced transformation with "last\next + a temporal noun" is relevant to "in recent years" also.
In the article, I. Yoo uses the terms "deictically anchored coding time" vs. "undeictically anchored predicated time". (see deixis at Wikipedia)