AUDEMARS PIGUET’S Ultra Thin Perpetual Calendar

Hiren Kumar Bose on the bare specifics of Audemars Piguet Royal Oak Perpetual Calendar UItra Thin, a world’s first

What’s So Cool About It: With a movement of 2.89 mm in thickness and a case of 6.3 mm in height, the watch becomes the world’s thinnest automatic perpetual calendar wristwatch. Not only is the new movement thinner, it is also simplified, being made up of 256 components. Reducing the height of the movement so significantly meant the movement grew sideways—measuring 29mm in diameter.

The Dial: Simplified than its earlier cousins it’s lighter and less cluttered. The dial is dark blue and finished with vertical brushing, making the hands and hour markers more prominent. Experts consider it wise since the dial has more sub-dials than the ordinary Royal Oak Perpetual calendar, with the additions of a day and night as well as leap year indicator that overlap with the larger sub-dials.

The Accomplishments: The watchmakers have filed two patents. The first concerns the date wheel that has an integrated end-of-month cam featuring a single irregular tooth which is deeper than the rest and advances the month disc by one increment at the end of the month. While the second redefines the 48-month wheel with a novel geometry using deep, curved grooves thus reducing the required tolerances of the levers, leading to a more reliable mechanism. The deepest grooves represent the month of February with 28 days, while the shallowest ones represent the months with 31 days. To indicate the leap year, the deepest groove has a corresponding notch that marks the February with 29 days. It is these two novel geometries that allow for a thinner calendar module. The movement has a frequency of 2.75Hz and despite its thinness, offers a respectable, albeit shortish, 40-hour power reserve.