T-G-I-F vs. S-H-I-T

A business man got on an elevator. When he entered, there was a blonde already inside who greeted him with a bright, "T-G-I-F."
He smiled at her and replied, "S-H-I-T."

She looked puzzled, and repeated, "T-G-I-F," more slowly.
He again answered, "S-H-I-T."

The blonde was trying to keep it friendly, so, she smiled her biggest smile and said as sweetly as possibly, "T-G-I-F."
The man smiled back to her and once again, "S-H-I-T."

The exasperated blonde finally decided to explain, 'T-G-I-F' means "Thank Goodness It's Friday". Get it, duuhhh?"
The man answered, 'S-H-I-T' means "Sorry, Honey, It's Thursday".

(from Dr. W)