Girl, and I think it isn't that bad, but isn't very good either. Sounds vaguely obtuse somehow... Day, dae, duheee.
In order
Jay - unisex. I had an aunt
Jay (greataunt? Grandaunt? whatever - she was born before 1900). I considered it for my son - I like it for girls but would only use for a boy
Ray - boy only - what a cool name.
Rae for a girl, but I don't care for that.
Kay - girl. Like
Jay, it's sort of a letter name, but substantial enough.
May - girl. The image of the month is too mild and sweet for my taste and the word may is a problem IMO but the name is alright. NMS.
Day
Fay - don't like it. Suggests fairies, goofy. Or, retro like
Fay Wray? It's ott somehow, nmsaa.
Gay - a legit girl name with a nice meaning, just sort of obsolete.
Tay - childish nick for
Taylor, ugh. unisex
Bay - horsey.