One of the things we all have to struggle with on an everyday basis is the clash between expectations and reality. As we see from Oedipus Rex to modern-day lasagna memes, life’s protagonists will never cease to swim bravely out into the great sea of hopeful optimism only to be battered back to shore by the tides of FML.

Civil time is one of the biggest examples of humans trying to wrestle reality into the neat little box of their expectations. We all know that not every day is exactly 24 hours long. It varies by about 30 seconds either way.

(Those of you familiar with the equation of time watch function may be wondering about the -16 +14 scale — hold that thought.)

The 24-hour day is constructed on an astronomical model that has Earth moving around the Sun at a constant speed, with a perfectly circular orbit centring on the Sun, rotating on an axis perpendicular to its orbit. Guess how many of those things are true? Hint: it’s zero.

So, we have these teeny tiny discrepancies between the 24-hour day, and the actual day (the time it takes for the sun to come round to the same spot in the sky consecutively). Up to 30 seconds either way, like we mentioned above.

Over the course of a few weeks, these little discrepancies add up and one day you look at your watch at noon but then you realise the sun is still quite a ways off reaching its zenith, and you think WTF is going on? My friends, the equation of time is what’s going on.

Do you see? The equation of time is not the difference between the solar and civil day, as it is frequently and glibly said to be. (Mea culpa: I used to say this too.) It is the cumulative lag or gain that a given solar day has with reference to its corresponding civil day, caused by the difference between the solar and civil day. If the equation of time is total debit/credit, then the difference between solar and civil time is daily spend/income.

Which brings us to the Breguet Marine Équation Marchante. It’s a big deal having the equation of time on a watch. What makes the running equation of time any more special?

Basically, there isn’t much of a consensus regarding the indication of the equation of time. Some institutions take the negative reading to mean that civil time lags behind solar time; others take it to mean the reverse. In any case, it’s not hella precise, and we won’t stand for that in high watchmaking, thank you very much.

The running equation of time displays information in a highly intuitive display, with a separate hand that runs behind or ahead of the civil time reading. No confusion there. This isn’t the first time the running equation of time has appeared in one of Swatch Group’s prestige brands — the complication has made prominent outings in the key collections of Blancpain, both Villeret and Le Brassus. In fact, it was the 2006 Blancpain Le Brassus Équation Marchante that premiered the running equation of time in a wristwatch.

Compared to the exceptional classicism of the Blancpain watches, however, the Breguet Marine Équation Marchante is sprightly and contemporary, built on the automatic ultra-thin tourbillon movement that we first saw in 2012’s Classique Chronométrie 7227. Instead of the blisteringly fast 10Hz balance we saw in that watch, the Breguet Marine Équation Marchante has a toned-down 4Hz (28,800vph) balance.

Between the tourbillon and the upper tourbillon bridge is the equation of time cam, with its familiar peanut shape. The nickel-phosphor cam is grown on a sapphire crystal disc using LIGA processes, and the sprung feeler which transmits information to the equation of time hand travels freely along the inside edge of the openworked cam.

Because the cam is formed through electroplating, very precise shapes can be achieved — accounting for the slight irregularity in the surface of the cam right around the February mark. That little kink is there to accommodate the leap year when there is an extra day in the month of February. Most equation-of-time cams are finished by hand, so the profile of the cam follows the line of best fit.

The high surface quality of LIGA components makes hand finishing unnecessary, however, so the cam takes the most precise shape possible.

Housing the equation of time in a watch from the Marine collection is also singularly appropriate, since astronomical complications are closely tied to the advent of maritime navigation and exploration. In keeping with the theme, the bridges of the movement have been engraved with a depiction of a French naval vessel, the Royal Louis. The ship displays a standard patterned with fleurs-de-lis, indicating that royalty is on board. I was told the member of royalty here would be Louis XVIII. I don’t really know how I feel about having an engraving alluding to the Bourbon Restoration alongside a date of the Republican Calendar (7 Messidor, An 9), but I’m not a historian, so it doesn’t bother me in any case.

The Breguet Marine Équation Marchante is one of those rare instances in life where reality exceeds expectations. So maybe the engraving of the Royal Louis is meant to show that the judicious application of tradition and expertise is all you need to cut through the tides of FML.