I'm guessing there are very few women alive who have not dealt with this at one time or another. I can think of at least 10 friends I have who have all shared the same story - "My first period happened in grade school on a day I was wearing white jeans."
My periods are so random, I am NEVER prepared for them. I've ruined more than a few pair of undies that way. My mother was on a long flight to Greece back in the 70's when hers started. The staff didn't have any pads available - they ended up trying to quietly query female passengers to see if anyone had a few.
Last comment on periods and pads -
Have you ever been in a bathroom and had another woman ask, "Can I borrow a pad/pon?" I always think to myself, "Borrow? What, like I want it back when you're done with it?!"