Today's author: Mark Gillis is an Excel writer. He was born October 3, 1952. Does his birthday fall on the same weekday as your birthday? Do you have nagging, unanswered questions floating around in the back of your mind like: "What day of the week does the date, January 23, 4589 fall on?", "What's the date of the eighth Thursday of 1922?", and "Is 9000 a leap year?". If you're like me, the answer is clearly no. Nevertheless, there's a remote chance that...