How to Build (and Buy) a Leap-Year-Proof Watch

There's little more annoying than looking down at your fine Swiss timepiece and realizing it's wrong. If you're going to survive next week's leap day without any horological hitches, you're going to want a perpetual calendar strapped to your wrist. A perpetual calendar is a watch that tracks the date and doesn't need to be adjusted for the different lengths of the months or for the leap day every four years. The only time most perpetuals need adjusting is every 100 years, when we skip a leap year. Most of these timepieces show you the date, day of the week, month, phase of the moon, and even the year within the leap-year cycle.