The TONDA PF Hijri Perpetual Calendar is a horological expression of the Tabular Islamic calendar developed by Muslim scholars and astronomers in the 8th century. This system made it possible for historians to convert Islamic dates to Gregorian dates, which in turn has made the Hijri Perpetual Calendar possible. The first year of the Hijri calendar corresponds to the year 622 CE and is marked by the Prophet Muhammad’s Hijrah (Arabic for “migration”) from Mecca to Medina in what is today Saudi Arabia.

The lunar Hijri calendar is based on the cycles of the moon, in comparison to the solar Gregorian calendar and lunisolar Chinese Xiali calendar. This makes for a 30-year cycle with each year consisting of 12 months that are 29 or 30 days long. In each 30-year cycle there are 19 common years of 354 days and 11 abundant years of 355 days.

The new TONDA PF Hijri Perpetual Calendar has a 100m water-resistant stainless-steel case with alternating satin and polished finishes. Its signature fluted bezel is in 950 platinum, paired with a matching stainless-steel bracelet with folding clasp.

The viridian green dial is hand-finished with a Grain d’Orge guilloché. The applied hour markers and skeletonized delta hour and minute hands are crafted in 18ct gold with rhodium plating. The second hand and calendar subdial hands are made of rhodium-plated steel.

The TONDA PF Hijri Perpetual Calendar is equipped with the Caliber PF009 automatic movement, which operates at 28,800 vibrations per hour (4 Hz) and has a power reserve of 48 hours. The intricate movement has beveled bridges. The skeletonized rotor is chiseled from platinum with a polished and sandblasted finish. Like the case and dial, it is meticulously finished with Côtes de Genève and perlage throughout.

The TONDA PF Hijri Perpetual Calendar displays all the information on the dial. The 12-hour subdial shows the 30-year cycle with the abundant 355-day years in beige and the standard 354-day years in white. The 3 o’clock subdial indicates the numbered months of the year with the ninth month of Ramadan highlighted in bright red. The 9 o’clock subdial shows the days of the month with an aperture indicating whether it is a 30-day abundant month or a 29-day common month. A white aperture indicates a 29-day month. The activated beige aperture indicates a 30-day month, with the number 30 in beige and written in Arabic as ۳۰.

Finally, the 6 o’clock subdial features the blue aventurine moonphase display, which shows the position of the moon in the northern and southern hemispheres.