"TGIF"

A couple works in the same building. After work one day they both were riding down in the same elevator together.The wife says to her husband"TGIF"...he replies with a "S.H.I.T." Puzzled she repeats the same and husband responds with same reply. The wife says,"Didn't you hear what I said? TGIF: Thank God It's Friday!" Her husband says, "Yes and I said S.H.I.T: Sorry Honey It's Thursday."