If you feel a little odd today, your calendar might explain why. Today’s date, 9/11/13, is a mathematical phenomenon so rare that it only occurs five times every 100 years. This is the last time for ...

SAN FRANCISCO – Ron Gordon would like you to take a moment or three to think about what an odd day Saturday is. Why? Because 7/9/11 is one of only six dates this century that features three ...