Solution for #28

Crossing the border, Hans and Fritz were required to fill out a personal information form, which asked, among other things, their birthdays. The German date ordering is day/month/year, rather than the American way, month/day/year. Fritz was born on, say, July 7th, so he wrote down 7/7/15 -- no problem. Hans was born on, say, July 20th, so he wrote down 20/7/15 instead of the American way, 7/20/15. Since Hans had claimed to be a returning American, he was found out by the border police.