"T.G.I.F" joke

A Blonde is getting on an elevator and meets a gentleman on
board.
"T.G.I.F." she says.
"S.H.I.T" was his reply.
Puzzled she replied "T.G.I.F"
The gentleman was getting a little disturbed the the remark, so
he says again. "S.H.I.T.".
The Blonde leans over and whispers "THANK GOD IT'S FRIDAY".
The gentleman responses with "SORRY, HONEY IT'S THURSDAY".