The annual calendar is a complication invented by Patek Philippe.

While it plays second fiddle to the perpetual calendar in the minds of most collectors, the reality is that the construction of this calendar mechanism is by no means a simple feat, and requires impressive micro-engineering and design acumen to execute well. Able to account for months of different lengths, it only requires manual adjustment once per year — at the end of February. 

However, this is no ordinary annual calendar: A Reference 5905P-010 from circa 2019, it also includes a flyback chronograph — one in which a single button press both stops and instantaneously restarts the chronograph. Convenient for timing laps, this complication proves unbeatable when combined with the utility of an annual calendar.

This particular 5905P-010 is housed in a 42mm platinum case with a signed crown, square pushers, a polished, concave bezel, and a sapphire crystal. It features a luminous glossy black dial with applied indices, a white minute track with a radial subsidiary register, a matching luminous ‘obelisk’ handset, date, month, and day apertures, and a running seconds sub-register above 6 o’clock. 

Flip the watch over, and one is greeted — via a sapphire exhibition caseback — with a view of the automatic Patek Philippe Calibre CH 28-520 QA 24H movement. Paired to a 21mm, signed black alligator leather strap with a signed, platinum pin buckle, this is simply a stunning timepiece in every regard: horologically, aesthetically, and functionally. Moreover, it includes its factory goodies.

If you’re the type of collector who only has eyes for the best, then this watch is for you!