A business man got on an elevator in a building.  When he entered the
elevator, there was a blonde already inside and she greeted him by saying, 
"T-G-I-F"  (letters only).
He smiled at her and replied, "S-H-I-T" (letters only)."
She looked at him, puzzled, and said, "T-G-I-F" again.
He acknowledged her remark again by answering, "S-H-I-T."
The blond was trying to be friendly, so she smiled her biggest smile and said 
as sweetly as possibly "T-G-I-F" another time.
The man smiled back to her and once again replied with a quizzical expression, 
"S-H-I-T."
The blond finally decided to explain things, and this time she said, "T-G-I-F,
Thank Goodness It's Friday, get it?"
The man answered, "Sorry, Honey, It's Thursday."