Happy Birthday to You is a traditional Earth song performed at birthdays.
In 2370, the crew of the USS Enterprise performed Happy Birthday to You for William Riker. (TNG short story: "A Q to Swear By")
After suffering a coma after a Lethean attack, Julian Bashir was treated to a perfomance of Happy Birthday to You by a representation of Elim Garak in his mind. (DS9 episode: "Distant Voices")