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.'
> 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'