Consider a date and time in YY-MM-DD hh:mm format with hh a 24-hour range. What is the first date in a century where all digits are different?
Submit your answer to Gene Wirchenko <email@example.com>. Your answer should be in the form of a proof. That means to show how your answer must be correct. The deadline is Wednesday, August 24, 2016 at noon Pacific Time. I will post the answer shortly after.