T.G.I.F.

A guy walks into an elevator, pushes the button for his floor and then notices a perky little blonde is in there with him.
He smiles at her and she smiles back and says T.G.I.F....he thinks for a minute looks back at her and says S.H.I.T.
The blonde being so pleasantly perky looks at him again and with a little more enthusiasm repeats T.G.I. F.
He again looks at her a little puzzled and says again S.H.I.T.
This time the little perky princess prepares her biggest smile and musters all the excitement she can and repeats T.G.I.F.
By this time the guy is more than annoyed with her and mockingly exclaims S.H.I.T....by now the blonde is a little confused and says with a smile T.G.I.F. means "Thank God It's Friday duuuuhhhh".
Waiting for the guy to "get it" to which he turns to her and says sternly "S.H.I.T. means Sorry Honey Its Thursday....duuuhhhh"