This year on January 12th, they celebrated their 21st anniversary and played several songs from their early years during the day.

Oldest song I usually hear occasionally is Baby One More Time by Britney Spears. Otherwise it usually is 2005-era Fall Out Boy or Panic At The Disco.

When it was new, the oldest songs they played were Under The Bridge by Red Hot Chili Peppers and Kiss by Prince (1986 and 1991 respectively)

CHR stations in general, especially 103.7 in Milwaukee which never got over their crunk phase in 2003-2004 have been playing songs that are older and older. The audience for CHR seems like it is getting less and less younger and more adult .