Humble Pi: When Math Goes Wrong in the Real World

by Matt Parker

In 46 BCE Julius Caesar decided to fix this with a new, predictable calendar. Every year would have 365 days—the closest whole number to the true value—and the bonus quarter days would be saved up until every fourth year, which would have a single bonus day. The leap year with an extra leap day was born! To get everything back into alignment in the first place, the year 46 BCE had a possible-world-record 445 days. In addition to the bonus month between February and March, two more months were inserted between November and December. Then, from 45 BCE onward, leap years were inserted every four years to keep the calendar in sync. Well, almost. There was an initial clerical error, by which the last year in a four-year period was double-counted as the first year of the next period, so leap years were actually put in every three years. But this was spotted, fixed, and by 3 CE, everything was on track.