FFS day Share definition Flag The official day to fuck your friends sister.On November,22 is National FFS day Me:Hey bro wheres your sister.My friend:idk why?Me:Dont you know today is national FFS day FFS day by Dxddycolt34 November 21, 2019 0 0 Get merch Get the FFS day mug. Buy Now — $32.95 See more merch