Annual Calendar - Brief History

Brief History

Ancient calendars (static) may always have been annual, even after the length of the calendar year was fixed at (avg.) 365.25 days by the Julian Calendar (46 BC). Early Romans observed an 8-day market week, called the nundinal cycle, until the seven-day week was adopted during the reign of Emperor Constantine the Great (306-337). When the number of days in the year is not evenly divisible by the number of days in the week the calendar is annual, since a representation of one year will not serve to represent the succeeding year. A goal of modern calendar reform has been to gain wide acceptance of some form of perennial calendar, based on a typically 364-day year. This would secure a number of benefits related to simplicity of annual scheduling, though there would also be noteworthy disadvantages.

In the world of watchmaking, the first annual calendar indicator introduced for a wristwatch was patented in 1996 by Patek Philippe. Today, along with the moon phase and power reserve indicators, it is one of the most useful features of any timepiece. Since 1996, the mechanism of an annual calendar was continuously improved. It is now used in watch manufacture by several watchmaking companies. The annual calendar is not a common feature. It can be found in: Breitling (Navitimer Olympus), Bvlgari (Bvlgari Annual Calendar), Ulysse Nardin (Marine Chronograph), Patek Philippe (Ref. 5035, 5135, 5146, 5147, 5396 and 5960), and Zenith (Captain Winsor).