How do you usually calculate the average leap year? My usual method is to check the number of days in February of the current year, 28 days is a normal year, and 29 days is a leap year (of course, it is not the most rigorous method). In the watchmaking industry, the perpetual calendar function is very professional. It means that the watch has the function of displaying the date, week, and month, and can automatically adjust the size of the month (31 days or 30 days) and the 28 days or 29 days of February. day to adjust. Some watch fans are very partial to perpetual calendar watches, thinking…