Calendrier Hégirien Trentenaire Continu

The clock with a thirty-year continuous lunar calendar 

"The calendar is an eminently fascinating watchmaking complication, as it really is the mirror of civilisations", Michel Parmigiani. 

Never before in the history of watchmaking has a Hegirian mechanical continuous calendar been invented by a Swiss Haute Horlogerie company. The only one of its kind in the world and achieved after many years of research, the Parmigiani thirty-year continuous lunar calendar clock indicates the time over a lunar cycle lasting 30 years, alternating the 19 normal years with 11 leap years. Based on the ephemerides from the Paris Observatory, Parmigiani Fleurier's thirty-year lunar calendar is theoretical as it is based on the observation of the celestial mechanical movement. 

The lunar calendar, a base shared by the Hegirian or Islamic calendar, is calculated on a year of 12 lunar months, each alternating either 29 or 30 days. The Hegirian year, shorter than the Gregorian year, has 354 or 355 days. This difference, due to the last lunar month which contains 29 or 30 days, determines the years known as "normal" years with 354 days and the 'leap' years which have 355 days. The most common thirty-year periodical lunar cycle alternates 19 normal years with 11 leap years. These leap years occur on years 2, 5, 7, 10, 13, 16, 18, 21, 24, 26, and 29. 

The lunar month starts when the moon is in line with the sun when seen from the earth, known as the conjunction. The month is defned as the average duration of one orbit of the moon around the earth (approximately 29.53 days). But to the naked eye, the frst crescent of the moon may be visible from Morocco but not from Kuwait. 

A technical feat 

The frst studies and the registration of the patent for the continuous thirty-year calendar had already been orchestrated by Michel Parmigiani and date back to 1993. Inspired by a restoration that he carried out on a simple Hegirian calendar, Michel Parmigiani then successfully led this study which can now be counted as an absolute world frst, as no lunar calendar had ever been designed to operate continuously. Requiring no intervention from the user, the continuous calendar automatically corrects the lunar cycle. In addition, the clock offers a choice of two leap year cycles. The user simply needs to know the type of calendar used in the current location, and to set the clock accordingly.  

This extraordinary invention is a milestone advancing the understanding and development of a  Hegirian calendar and paying tribute to the Islamic calendar.  

The Parmigiani clock, which has an autonomy of 30 days, has been produced exclusively in the  Haute Horlogerie brand's own workshops. Its dial shows the hours and minutes, the date in Arabic  numerals, the day of the week and the month in Arabic calligraphy, the leap years in Arabic  numerals and the normal years in the form of indices, the precision moon phases and the power  reserve.  The cabinet and base are made from solid silver, with decorative details in black obsidian,  quartz and ruby. Ten of these clocks, all created with a unique fnish and aesthetic, will be available  to the public.