Dear Sir or Madam,
Apparently it falls to me to clarify the definition of the word "classic." As a noun, a "classic" is defined by Meriam Webster as: " a work of enduring excellence," or " a typical or perfect example." As an adjective, it is defined as " serving as a standard of excellence : of recognized value." In neither usage does it refer to "any song which is older than the legal drinking age."
Let me give you an example. The song "Yesterday" by the Beatles is considered to be a classic of pop music. It has been enjoyed by persons of taste for over 40 years. It can be said to have "stood the test of time."
"Piano Man" by Billy Joel, on the other hand meets none of the criteria for being considered a "classic." No one has ever listened to the song "Piano Man" and thought, "now there is a work which will be appreciated and enjoyed for generations to come. Rhyming Davy with Navy? Classic Joel! Oh, and the chorus? La-diddy-da-diddy-da? Brilliant! Surely this magnum opus will be a welcome addition to the canon for decades!"
If you want to play both the Beatles and Billy Joel, you are certainly free to do so. You could play both Bob Dylan and Bobby Brown if you wish. You could follow Chuck Berry with Katy Perry, it's your station, you can play whatever you like. But then you don't get to call it "Classic Hits." Just call it "Music." Words mean things.