Antide Janvier, 1751-1835, was born in Briva, France, the son of a farmer. His aptitude for mechanics and science meant that at an early age he was sent to the Abbée Tournier where he obviously excelled for by the age of fifteen he had already made a complicated astronomical clock with mean, solar and sidereal time and incorporating an orrery, an achievement well beyond most competent and experienced clockmakers. By the age of nineteen the already famous prodigy presented Louis XV with an even more complicated astronomical clock. By 1784 he was appointed clockmaker to Louis XVI and given residence at Loges aux Menus Plaisirs.
In France in 1793 the Revolutionary government ordered decimalisation of the systems of measurement, including time. The new time divided the day into ten hours and the hours into 100 minutes. This was paralleled by a new system of Revolutionary months, each named after a natural attribute of the season and divided into three 'decades', each of ten days. The twelve months of thirty days gave a year of only 360 days so the five extra days were national festivals, the leap year day being the Festival of the Revolution. The degrees suffered the same fate and were divided into four quarters of 100 degrees.
As this form of timekeeping took some getting used to, Janvier's clocks showing the new revolutionary time, also showed mean time as on the present example. As it turned out this was most wise for the decimal system soon lapsed with the rise of Napoleon and the establishment of the Empire