That's tomorrow, Saturday, Apr. 19. Your day to celebrate the old way of buying music, where you got into your car and drove to a local store and talked to the clerk and sifted through the racks and maybe experienced the delight of finding an old CD you'd forgotten about, heavily discounted or expensive and rare. Or maybe you heard a great tune spinning in the background and bought it, like I did with The Monochrome Set's Strange Boutique and PiL's Second Edition and Wilco's amazing live CD (their best album, in my opinion), Kicking Television.
Anyway, a lot of stores are having special events--for example, Seattle institution Silver Platters, which started selling CDs (and Laserdiscs!) back in the early 80s when vinyl was still the norm, is having live music all day long. So if you love music, throw your local record store a bone and buy a disc or two.