Side Piece day
February 15th The day men take there side piece(the other girl he is dating on the side) out as if it were Valentines day.
Tommy bought 2 bouquets of Roses One for his girlfriend on Valentines day and one for his side piece on side piece day.
Side Piece Day
Celebrated the day before (February13)or the day after (February15) Valentines day. A day men spend with their side piece as if it was Valentines Day.
I was with my other girl on Side piece Day