The widely used Gregorian calendar was introduced in 1582 by Pope Gregory XIII in replacement of the Julian calendar. The new system adopted the year of 365 days with a leap year of 366 days every 4 years that had already been fixed by Julius Caesar but it revealed to be inexact. Therefore Pope Gregory ordered a calendar reform with a correction of 10 days, whereby the 4th October 1582 of the Julian calendar was immediately followed by the 15th October 1582 of the Gregorian calendar.
He introduced also a special secular leap year cycle, i.e. only those secular years which are divisible by 400 are considered to be leap years. Therefore the secular years 1700, 1800, 1900, 2100, 2200, 2300 are not leap years and have only 28 days in February.
Watches with perpetual calendar usually have the normal leap year cycle. Exceptions are big astronomic clocks as well as two pocket watches made by Patek Philippe, one is the Calibre “89” and the other is a watch that was made in the seventies for an American collector. Those are already provided with a secular cycle.
Introduced in 1996, “PERPETUEL SECULAR CALENDER” Wristwatch by Svend Andersen Genève is considered as the first hundred percent perpetual calendar wristwatch.
The “PERPETUEL SECULAR CALENDER” Wristwatch is provided with a four years’ programme for the leap year cycle: a wheel with 48 teeth = 4 x 12 months, thus every 4 year the 29th February appears.
This wheel pushes a reduction wheel one tooth forward every 4 years. The reduction wheel divides the turning speed into two and hereby the secular wheel of 50 teeth is activated and moves on for one tooth every 8 years, e.g. 50 x 8 = 400. Thus, the secular wheel turns once in 400 years and is programmed for the future secular years: 2000 (with 29 Feb.), 2100 (28 Feb.), 2200 (28 Feb.), 2300 (28 Feb.) and 2400 (29 Feb.).
This is how the mechanical invisible under-dial life of the “PERPETUEL SECULAR CALENDER” Wristwatch works. In order to make these perpetual calendar functions visible and legible, the back side is provided with three dials:
Left: in black and blue, the 4 years’ leap year cycle
Centre: the central hand showing 50 years in green; it turns 2x per century, e.g. 1996 shows 46 + 50 = 96
Right: in blue and red, the 400 years’ secular cycle.
Diameter : 40 mm
Thickness: 11 mm
Available in White/Pink Gold
Automatic chronometer movement