Equation of time

The equation of time is the difference between mean solar time – our civil time based on a conventional twenty-four-hour period – and the true solar time, which varies with the earth’s irregular orbit round the sun.

Equation of Time

From time immemorial, the Sun has served as the basis of time measurement. Nonetheless, the visible orbit of the Sun – the true solar time shown on sundials – is irregular.

The equation of time is the difference between mean solar time – our civil time based on a conventional twenty-four-hour period – and the true solar time, which varies with the earth’s irregular orbit round the sun. Mean solar tune runs up to 16 minutes behind true solar time, as is the case on November 3; or up to 14 minutes ahead of it, as is the case on February 12. The two values are exactly matched on just four days a year.

Appointed "Chronometer-maker to the French Royal Navy" in 1815, A.-L. Breguet and his son created the most elaborate equation of time models of their time.

Marine Équation Marchante 5887

The new Marine Équation Marchante 5887, a Grandes Complications watch, features a running equation of time, a perpetual calendar and a tourbillon.

Rare and fascinating, the running equation of time displays civil time and true time simultaneously, with the help of two distinctive minutes hands.

A.-L. Breguet was the first to introduce guilloche decoration to watch dials. Today, Breguet continues this tradition by hand-turning the gold dials on rose engines. The dial of this new Marine Équation Marchante 5887 has an exclusive type of engine-turning in "wave" pattern, especially developed for this piece. 

Models with this invention

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