From a radio programming standpoint, the "0" years aren't necessarily the hard and fast dividing point between decades. And that is because of listener perceptions.
Examples, using the format I know best, The Eighties Channel™:
"Heart of Glass" by Blondie is a song that a lot of listeners will swear up and down was released in the 1980s. It actually peaked in April 1979. Similarly, "One Way Or Another" peaked in August of that year.
The song so many associate with that decade because it was the first video shown on MTV -- "Video Killed The Radio Star" by the Buggles -- peaked in December 1979. In my opinion, if MTV had not chosen that for the launch, it would have remained an obscurity.
"Don't Bring Me Down" by ELO ... 80's song, right? Nope, peaked in September 1979. Other biggies that were released in that year but peaked in 1980: "Ladies Night" by Kool & The Gang, "Heartbreaker" by Pat Benatar, "Funkytown" by Lipps Inc., "Don't Do Me Like That" by Tom Petty & the Heartbreakers and "Rock With You" by Michael Jackson.
Speaking of Tom Petty, his "Free Fallin'" was released in 1989 but peaked in January 1990. Similarly, "Black Velvet" by Alannah Myles, which peaked in March 1990 and "It Must Have Been Love" by Roxette (peaked in June of that year).
And the misperceptions aren't confined to just that threshold ... I have had people swear up and down that Gary Numan's "Cars" was a hit in 1982 ... it was June 1980.