In the night of October 24 to 25, 2026, France set its clocks back by one hour, and the debate over daylight saving time resurfaced as every autumn. In 1793, the country had, however, attempted something far more radical: to change time itself. The National Convention decreed a day of 10 hours, each hour divided into 100 minutes, and those minutes themselves divided into 100 seconds.
- The Convention decreed in 1793 a day of 10 hours, each hour of 100 minutes.
- Clockmakers produced double-dial watches to read both systems.
- The obligation to decimal time was suspended on 7 April 1795, after 197 days.
A Day of 100,000 Seconds
Everything started with a decree from the National Convention dated October 5, 1793 and completed on November 24, 1793, which is to say the 4th Frimaire Year II, establishing the Republican calendar. Its Article XI targets the dial. From midnight to midnight, the day is divided into 10 parts or hours, each part subdivided into 10 others, and so on down to the smallest measurable duration. The 100th part of an hour takes the name “decimal minute,” and the 100th part of a minute is the “decimal second.”
The conversions are dizzying. A decimal hour equals 2 hours 24 minutes, a decimal minute equals 1 minute 26.4 seconds, and the entire day counts 100,000 decimal seconds, compared with the 86,400 seconds of the system we still use.
In this new dial, noon fell at 5 decimal hours. An appointment at 3 decimal hours corresponded to 7:12 a.m., and one at 6 decimal hours to 14:24. For a craftsman who anchored his day to church bells and his pocket watch, it meant reworking all of his reference points.
Article XI did not become mandatory until 1 Vendémiaire Year III, that is, September 22, 1794.
Double-dial watches, then a bill deemed too heavy
Watchmakers did not wait for the obligation to push ahead with adaptations. They produced watches and wall clocks with two dials, one graduated 1 to 10 for the new hour and another 1 to 24 for the old. The public could thus read both systems at a glance, giving them time to grow accustomed. Laplace, one of the era’s greatest scientists, used a decimal watch himself.
The habit never truly took hold. On March 1, 1795, a report presented to the Convention highlighted the enormous cost of changing clocks as well as the confusion felt by citizens and watchmakers. A few weeks later, the law of 18 Germinal Year III, i.e. April 7, 1795, suspended the mandatory use of decimal time. This same law also laid the groundwork for the metric system, which lends the scene a double verdict: maintain measures of length and weight, but loosen those of time.
The tally is simple: 197 days of obligation, from September 22, 1794 to April 7, 1795.
The metre won, the hour lost
The two reforms were twin efforts, launched in a sweeping push to reset conventions. The metre has endured through the centuries and spread well beyond French borders. The 100-minute hour, by contrast, never progressed beyond the experimental stage. A dial is read ten times a day, shared with neighbours, merchants, travelers: changing it requires everyone to change at the same time.
The 1795 suspension did not erase every trace. In some towns, civil records continued to be written in decimal time until September 1800. In Toulouse, the Capitole retained a decimal clock. At the Tuileries, two of the four dials displayed decimal time at least until 1801, that is six years after the end of the obligation.
These local survivals tell something that the decrees do not. When a rule becomes optional, those who adopted it have no reason to dismantle their clock overnight, especially if remaking it is costly. The same 1795 report that highlighted the cost subtly explains why some dials eventually remained in place.
The contrast with today’s clock changes is striking. Moving the hands forward or backward by 60 minutes twice a year preserves the same second, the same minute, and the same hour. The Convention, by contrast, asked to redraw each of these units. When you compare the scale of the two, the shift of that late October weekend feels like a precision adjustment.
One uncertainty remains: for the Tuileries, sources mention 1801 “at least,” which leaves the exact date when the two decimal dials ceased to strike Parisian eyes open to interpretation.
Sources: france-pittoresque.com | shs.hal.science
