Sometimes perpetual calendars are too complicated but a simple calendar just doesn’t cut it anymore because nearly half the months have less than 31 days, making it five adjustments a year too many for some. But don’t fret, there is a middle ground between the most basic calendar watches and complex perpetual calendars: the annual calendar automatically adjusts for each month with 30 or 31 days, meaning just one adjustment per year for the owner in February. Here’s a brief history of the complication.