so last year

so last year

Said of something that was previously fashionable or trendy (whether or not in the actual previous calendar year) but is not any longer. A: "Hey, I finally got those decals on my car that everyone was going crazy for!" B: "Pfft, please, those are so last year. No one cares about those any more!" A word of warning from our fashionistas—bell bottoms are so last year! If you want to look your absolute best, the new hottest craze is ruffled puffy shirts.
See also: last, year
Farlex Dictionary of Idioms.

so last year

n. outdated. That outfit is so last year!
See also: last, year
McGraw-Hill's Dictionary of American Slang and Colloquial Expressions
See also:
  • vogue
  • (something) is the new (something)
  • is the new...
  • the in thing to do
  • the new rock and roll
  • go out of style
  • go out of fashion
  • out of style
  • out of fashion
  • laine
References in periodicals archive
Nearly two-thirds (64 percent) of those surveyed said they expect an increase in next year's volume compared to 56 percent who indicated so last year and 47 percent who indicated so in 1992.