Decimal time

The question of adopting a decimal (base 10) system of time has been raised many times for two centuries. It gained considerable support after the French Revolution in 1794, as the metric system was being established around 1900, and again in the 1980s as computers were becoming popular.

The practical implementation of a division of the day and hour into 10-based units raises many questions. Considering the difficulty of adopting universal time based on hours from 1 to 24, the question of decimal time, which requires a complete transformation of all time systems, seems far-fetched.

Most decimal time systems would see the day divided into 10 hours and each of these divided into 100 minutes. Thus, there would be 1000 minutes per day, increasing the length of the minute by 44%. These hours would begin at midnight, with the work day starting at 3 and ending at 7, 20% longer than the current 8 hours.

This reveals the key issue with decimal time: It is not easily divisible by the ratios commonly used, including the convention of 3 "shifts" per day, each 8 hours long. An even decimal-denominated shift would be 3 hours 33 minutes long, an impractical unit of measure. The length of decimal hours is also not conducive to usual human activities, so they would have to be subdivided for practical reasons.

History

The idea of decimalizing time is not new. In 1794, on August 22, the National Convention in France issued a decree prescribing the use of decimal measures throughout the entire Republic. Clockmakers had to comply with this decree, and they adopted special dials showing both 24-hour time and decimal time for watches, clocks, and church clocks.

The Convention opened a competition to determine the simplest, most robust, and least expensive organization to give to timepieces designed to measure different parts of the day according to the decimal system. A commission was appointed for this purpose, and the jury was composed of Ferdinand Berthoud, Lagrange, Lepaute the elder, Antoine Janvier, Lépine the younger, and Mathieu the elder.

Despite the attempts of the Convention and clockmakers, the reform was not successful, due to the resistance of the population. The idea of decimal time predates the Revolution: Indeed, in the Encyclopédie Diderot, published in 1751, the following lines can be found: "It would be desirable that all divisions, for example, of the pound, sou, cloth, day, hour, etc., were in increments of 10; this division would make calculation much easier, more convenient, and would be preferable to the arbitrary division of the pound into 20 sous, sou into 12 deniers, day into 24 hours, hour into 60 minutes, etc."