A man walks into a bar

And sits down and announces to the bartender that he can tell the age of any scotch just by drinking it. The bartender thinks this guy is full of shit so he goes and gets the cheap 12 year stuff and pours a glass. The guy takes it, sniffs it, and takes a drink. He then proclaims, "well that's a 12 year old glass of scotch".

The bartender think it's just a lucky guess so he goes and gets a 20 year old bottle and pours the guy a drink. The guy takes it, sniffs it, and takes a drink. He then says, "oh well that's a 20 year old glass of scotch".

So now the bartender is kinda impressed so he goes into the back cabinet and gets a nice 45 year old bottle that he keeps for special occasions. He pours the guy a drink and then hands it to him. The man takes it, sniffs it, and drinks it. He proclaims, "well that's a 45 year old bottle of scotch!".

The bartender is now amazed and a small crowd is beginning to form. The bartender goes in the back room and takes out the 75 year old bottle of scotch. He pours the glass in the backroom so there's no chance this man can see the label. He hands the guy the drink and once again: he takes it, sniffs it, and drinks it. The man then correctly proclaims, "that's a 75 year old bottle of scotch!".

Now the bar is in a slight uproar and the man has a big grin on his face. A man from the crowd goes, "Hear try this one!". The man takes it and drinks it right away and exclaims, "ugh this tastes like piss!". The man from the crowd responds, "Good! Now how old am I?"