Glad you asked: it's PAYDAY for a lot of people!

Also, May 15th  is:
Peace Officers Memorial Day
National Chocolate Chip Day
National Nylon Stocking Day
National Endangered Species Day  (Third Friday in May only)
National Defense Transportation Day  (Third Friday in May only)
National Pizza Party Day  (Third Friday in May only)
National Bike to Work Day  (Third Friday in May only)
NASCAR Day  (Third Friday in May only)

MUSIC BIRTHDAYS:
EDDY ARNOLD (country singer) would be 97 if still alive
TRINI LOPEZ (“Lemon Tree” etc.) is 78
LENNY WELCH (“Since I Fell For You”) is 77
IAN AMEY (“Tich” from the British 60’s group ‘Dave Dee, Dozy, Beaky, Mick & Tich’) is 71
BRIAN ENO (Roxy Music) is 67
GARY THAIN (bassist for Uriah Heep) would be 67 if still alive
MIKE OLDFIELD (“Tubular Bells”)is 62