There are three people in a pub. Two of them are talking to each other.
They seem to be brooding. So they ask each other why they are brooding.
The first one says : "Well, I think it's because I have sex only once every
month."
Then the second one replies : "Oh, that's true". In my case, it's only once
every other month".
Then, they both look at the third guy, who seems to be very cheerful. They
are puzzled, so they ask him how often he has a screw.
"Once every six monthes" says the fellow.
"Then", ask the first, "why are you so happy?"
And the third replies "Because it's tonight !!!"