I collected the following a while ago. Pity I didn't note down the website so I can't toast to the writer. Anyway, I share it with you here now.
A teenager goes into a pharmacy. He's a little bit shy when talking to the pharmacist. "I'd like to buy some condoms" he says.
The pharmacists asks him, "Have you ever bought condoms before son?"
"Well, this is how it works," the pharacist says "We've got the three pack for when you are in high school. Friday, Saturday, Sunday.
"Then we have a 7 pack when you are in college - Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, and Sunday.
"Then we've got a 12 pack for when you are married. "January, February, …."