Why build a clock nobody wants?
A metre is one ten-millionth of the Earth's meridian. A litre is a cubic decimetre. Clean. Decimal. Universal.
Time stayed stubbornly sexagesimal: 60 seconds, 60 minutes, 24 hours, 7 days. The mismatch has frustrated reformers for centuries. A decimal clock would let you add 2.5 hours to 3.7 hours and get 6.2 hours without converting anything. Payroll, billing, scientific logging: all arithmetic on base-10 numbers. It sounds appealing.
Every attempt to impose it has failed.
French Revolutionary Time (1793-1805)
The most serious real-world experiment began during the French Revolution. The National Convention wanted to break with the old world entirely. New calendar. New week. New clock.
The decree of 24 November 1793 established a 10-hour day. Each hour had 100 minutes. Each minute had 100 seconds. A second under this system was 0.864 of a modern second. Clocks were manufactured with decimal faces. Public officials were required to use the new time. The Republican Calendar, its companion, renamed the months and abolished the seven-day week in favour of ten-day décades.
It did not stick. People kept using the old 24-hour clock in daily life. The decimal seconds were too short for practical precision. The 10-hour day made it hard to coordinate with neighbours who ignored the law. Napoleon abolished decimal time on 7 April 1805. France returned to 24 hours.
Swatch Internet Time (.beats, 1998)
Nearly two centuries later, the Swiss watch company Swatch tried again. In 1998 it launched Swatch Internet Time, a global decimal time that divided the day into 1,000 ".beats". One .beat was 1 minute and 26.4 seconds. The day started at @000, midnight in Biel, Switzerland, where Swatch is headquartered. No time zones. The same .beat number held everywhere on Earth at the same moment.
Swatch built .beats into its watches and partnered with websites to display the time. The pitch: a global, zone-free clock would simplify internet communication.
It failed commercially. People already had a global time standard (UTC) and their local wall clocks. Adding a third number with no connection to sunrise, sunset or lunchtime confused more than it helped. Swatch Internet Time never reached critical mass. No government, airline or stock exchange adopted it.
Stardates and decimal time in fiction
Fictional decimal systems have been more successful. Star Trek's stardate, introduced in 1966, is a floating-point number where each unit represents a fraction of a year. The original series used a 5-digit stardate. Later series refined the formula, but the core idea stayed: time as a single decimal number, not a clock face.
Stardates are not a real-world time system. No one uses them to catch a train. But they show the appeal of decimal time as a storytelling shorthand, a way to signal a future where time works differently.
Why decimal time failed
The rhythm problem
People organise their days around sunrise, lunch and bedtime. A 10-hour day does not map neatly to those rhythms. The French found that out when they tried to hold markets at decimal hours. Nobody came.
The coordination trap
Switching time systems requires everyone to switch at once. Clocks, software, schedules, legal documents: all need updating. The benefit of decimal arithmetic is dwarfed by the cost of changing every clock in the world.
No killer use case
For everyday life, adding 1 hour 45 minutes to 3 hours 20 minutes is not hard. For scientific work, seconds are already decimalised internally. The pain point is small. The fix is expensive.
Decimal hours: the one system that survived
One decimal time variant did survive: decimal hours. Instead of changing the day, decimal hours keep the 24-hour day but express minutes as a fraction of an hour.
15 minutes is 0.25 hours exactly.
30 minutes is 0.50 hours exactly.
45 minutes is 0.75 hours exactly.
7 minutes is 0.1167 hours exactly.
Why payroll needed it
Decimal hours survive because they solve a narrow, high-value problem: payroll arithmetic. An employer who clocks you in at 08:53 and out at 17:07 can convert 8 hours 14 minutes to 8.2333 hours, multiply by an hourly rate and get a clean dollar figure. No minutes-to-hours conversion. No rounding ambiguity. The system works within a single organisation without requiring society-wide change.
The US Fair Labor Standards Act has permitted time rounding since 1938, and most payroll systems now default to decimal hours. Lawyers use 0.1-hour increments (6 minutes). Project managers track tasks in decimal hours. The conversion is standard: divide minutes by 60.
The 7-minute rule
The "7-minute rule" is common in US payroll: round to the nearest quarter-hour at the 7-minute mark. Clock in at 08:07, it rounds to 08:00. Clock in at 08:08, it rounds to 08:15. The rounding must be neutral over time under FLSA rules. It is not a licence to always round down.
Common decimal-hour mistakes
0.5 hours is not 50 minutes. It is 30 minutes. That error is everywhere.
1.5 hours is 1 hour 30 minutes, not 1 hour 50 minutes. 0.25 hours is 15 minutes, not 25 minutes. The decimal point misleads people who are used to thinking in base-60.
Unix time: decimal seconds in computing
Computing took a different path. Unix time counts seconds since 00:00:00 UTC on 1 January 1970. It is a single decimal integer: the number of seconds elapsed. No hours. No minutes. No zones. Software developers add and subtract Unix timestamps directly.
Unix time is decimal in the same way a car odometer is decimal. It counts in base-10 units (seconds) but does not redivide the day. It avoids the social coordination problem because only machines use it. Humans still read wall clocks.
The 32-bit overflow of Unix time, the Year 2038 problem, is the price of that simplicity. Systems that store timestamps as signed 32-bit integers will roll over on 19 January 2038.
What anyone building a time system should learn
The history of decimal time is a story of good arithmetic losing to human behaviour. French Revolutionary Time lost because it disrupted daily life. Swatch Internet Time lost because it solved a problem nobody had. Decimal hours won because they changed nothing about the clock face and fixed a genuine pain point for payroll.
Anyone building a new time system should start with that lesson: people will not change how they read the day. Work around the clock, not against it.