EQUATION MARCHANTE MODEL, REF. 4238-3442A-55, CASE NO. 26⁄50

Amongst the most refined and elegant timepieces of the Blancpain manufacture, the present watch features an important array of complications, including an impressive equation of time display which allows the watch to follow the cycle of the sun. For convenience, humans have defined the day to be exactly 24 hours in length and watches that we know of are faithful to that definition regardless of their complication. In reality, however, the defined 24-hour day is a convenience, an average that serves most purposes well but does not correspond exactly to the actual length of a solar day. As the earth’s orbit is not exactly round and the earth’s axis of rotation is inclined by 23 degrees, the actual solar day may be several minutes longer or shorter, depending on the time of year, than 24 hours. The difference between the length of the actual solar day, termed “solar time”, and the 24-hour day, termed “civil time”, is called the equation of time. The accumulated differences between civil time and solar time can be as much as +14 minutes and –16 minutes; on four days per year the errors catch up and the solar time and civil time correspond exactly.

Blancpain was successful in mastering an innovative gear train that combines the running of the equation gear train controlled by a complex-shaped cam, and the running train of the watch’s civil minutes-hand to drive the running equation hand. This complication had been previously used in large clocks and pocket watches and is a skill that has been developed carefully over two centuries.