What Is Decimal Time?
Decimal time divides the day into powers of ten instead of 24 hours of 60 minutes. In the French Revolutionary system, a day has 10 decimal hours, each hour has 100 decimal minutes, and each minute has 100 decimal seconds, for 100,000 decimal seconds a day instead of 86,400. Reading decimal time is like reading a percentage of the day: 7:50:00 means the day is 75% over.
Decimal Time Conversions
| Decimal unit | Standard time |
|---|---|
| 1 decimal hour | 2 hours 24 minutes |
| 1 decimal minute | 1 minute 26.4 seconds |
| 1 decimal second | 0.864 seconds |
| 5:00:00 decimal | 12:00 noon |
| 2:50:00 decimal | 6:00 AM |
| 7:50:00 decimal | 6:00 PM |
To convert standard time to decimal time, divide the seconds since midnight by 0.864. To go back, multiply decimal seconds since midnight by 0.864.
A Short History
During the French Revolution, the same reforms that created the metric system also introduced decimal time. The National Convention adopted it in 1793 and its use became official in 1794, alongside the new French Republican Calendar. Clockmakers built dials with 10 hours, often showing both systems at once. But people never warmed to replacing every clock and relearning the day, and mandatory use was suspended in 1795, after only about a year and a half. The metric system survived; decimal time did not.
Swatch Internet Time
In 1998 the watch company Swatch launched another decimal idea: Internet Time, which splits the day into 1,000 “.beats” of 86.4 seconds each, with no time zones. Everyone in the world shares the same beat time, counted from midnight in Biel, Switzerland (UTC+1). The clock above shows the current beat too.