“Alwayz Into Something” by NWA mentions 1991 in the intro, or “Nineteen-ninety motherfuckin’ one” to be more exact. And from “California Love” by Dr. Dre and 2Pac:
Now it’s '95 and they clock me and watch me
Diamonds shinin lookin like I robbed Liberace
The Boomtown Rats managed it twice in the chorus of She’s So Modern:
She’s so twentieth century
She’s so nineteen seventies…
And to horribly date myself… me and my best mate were front row center and terribly impressed when Bob Geldof brought the band to Wellington and sang the updated lyric;
I thought it was interesting how the song Viva La Radio, although it doesn’t mention the year, dates itself by talking about carrying a radio around with her, since no one does that anymore with the advent of mp3 players.
“Christmas Wrapping” by the Waitresses: “Most of '81 passed along those lines.”
“Walking on the Sun” by Smash Mouth doesn’t mention a year, but a specific time gap: “Twenty-five years ago they spoke out”, referring to the protests of the late 60s. That pins the song to the mid-90s.