The A-Z of luxury watches: Why the perpetual calendar is the holy grail of complicated watches. 

In the pecking order of calendar complications, the perpetual calendar is unequivocally at the top of the list, besting such other variations as the annual calendar, the triple calendar, the day-date, and of course the simple date function. Such a movement displays the date, day, month, leap year, and sometimes the moon phase as well. But even among perpetual calendars, there are some which are more accurate than others.

Enter the secular perpetual calendar. As we know, perpetual calendars take into account the leap year cycle, so every four years it correctly displays 29th February instead of skipping to 1st March. But because of the imperfect alignment between the earth against the orbital path of the moon, there is no leap year every 100 years, and a secular perpetual calendar takes that into account as well, thus making it accurate to about 1,000 years as opposed to the usual 122.