Antide Janvier produced several clocks and regulators indicating the "Mouvement Périodique, Synodique et Journalier de la lune". He explained his reasoning in his book entitled "Recueil de Machines Composées et exécutées par Antide Janvier", 1828, pp. 23-25, pl. IX et X: "Several excellent workmen have often requested that I calculate a gear-train to indicate the raising and setting of the moon; some have shown me, quite proud of themselves, (clock cadratures under-dial works; striking-works; moion-works) giving the moving horizon the same variations as for sunrise and sunset; I have seen others that made the moon revolve in exactly 24 hours instead of the 24 hours 50' 28'' 20''', which make up the average lunar day. I have never been able to explain to them that the lines that determine the solar day, and of which the successive movements all take place within a year, could not be used to measure the lunar days, for which the same changes do not extend beyond one revolution of 27D 7H3' 4'', 6795, and that, in this manner, one would obtain only the average term between the various latitudes of the moon, whose orbit differs by 5 degrees on either side of the ecliptic on which the nodes retrograde with a speed of 6798D 4H 52' 5'', such that it would be necessary not only to take into consideration the periodic revolution of the moon, but also its revolution as compared to the nodes, to modify the movement of the horizon. One must possess a greater knowledge of celestial movemets than even the best watchmakers ordinarily have, to be certain of succeeding in such a task, and I sincerely doubt that those who undertake this work will gain much glory or even make the least profit by it, for I know better than anyone that this sort of machine does not lead to wealth."At the end of this somewhat unenthusiastic commentary Antide Janvier lists two tables of his calculations for the wheel trains necessary to show the periodic and synodic motions of the moon.A similar regulator, No. 406, is preserved in the Musée des arts décoratifs, Paris.Mean lunar time:The mean lunar (synodic) month is the average interval in days between exact conjunctions of the Moon and the Sun (as observed from the Earth). The time for the moon to make one revolution around its axis is 27.32166 "our" days. It is the same as the time to return to the same position among the stars, therefore it is called the sidereal month (sider = star in Latin). When the Moon is orbiting the Earth, the Earth is also going around the Sun; and while the Moon is completing its orbit, the Eartmoves a twelfth of the way around the Sun. This means that starting from a New Moon, the Moon has to go around a full orbit and a bit more to get back in between the Earth and the Sun again. The time it takes for the Moon to go from one New Moon to the next is called a Synodic Month, and equals 29.530589 days.