Why Time Isn’t Metric (and Why It Could Be)

Students sometimes wonder, "why doesn't the metric system have base-10 time?" It’s a great question, and an entirely reasonable one. If length, mass, and temperature all follow powers of ten, why does time stubbornly cling to 60s and 24s? Let’s explore the issue.

Why we don’t use base-10 time (the short answer)

The main reason is history, not logic. Our modern timekeeping descends from ancient Babylonian astronomy, which used base 60 because it has many divisors and worked well for fractions. When mechanical clocks, navigation, and later global coordination developed, they locked this system in place.

There was an attempt to change it. During the French Revolution, reformers introduced decimal time, but it failed. People didn’t want to relearn their daily rhythms, and the practical benefits weren’t compelling enough at the time. Once railroads, commerce, and science synchronized around the 24-hour day, the cost of switching became enormous.

In short: base-10 time lost not because it was wrong, but because it was inconvenient to adopt.

Why we should still consider base-10 time

Despite tradition, the idea remains attractive.

First, conceptual consistency. The metric system is elegant because everything scales by tens. Time is the odd one out, forcing students to juggle 60s and 24s alongside meters and kilograms.

Second, simpler mental math. In base-10 time, percentages map cleanly onto the day. Ten percent of the day is exactly one hour. One percent is exactly one minute. Scheduling, estimation, and proportional reasoning all become easier.

Third, modern technology removes old barriers. Computers already convert between units effortlessly. We no longer depend on gears and sundials. What once required hardware changes is now mostly software.

Finally, elements of base-10 time are already used by scientists. The SI base unit is the second, and we already use milliseconds, microseconds, and nanoseconds, pure powers of ten. Daily life is the only place where time remains stubbornly non-decimal.

A clean proposal for base-10 time

Here is a simple, human-usable base-10 system that keeps the length of the day unchanged:

• 1 day = 10 hours

• 1 hour = 100 minutes

• 1 minute = 100 seconds

That gives:

• 1 day = 100,000 seconds

• 1 decimal second ≈ 0.864 current seconds

Clock format would be straightforward: HH.MM.SS

Examples:

• 5.00.00 → exactly midday

• 2.50.00 → quarter-day

• 9.99.99 → end of day

In this system:

• 10% of the day = 1 hour

• 1% of the day = 1 minute

• Time becomes directly readable as a fraction of the day

Daily life would quickly normalize. Work might run from 3.33 to 6.67. Lunch happens at 5.00. Once learned, the system is arguably more intuitive than our current one.

Closing thought

Base-10 time is not a radical fantasy, it’s a coherent alternative that aligns better with how we already teach math and science. The real obstacle has never been feasibility, only familiarity. Asking why we don’t use it is exactly the right kind of question, because it reminds us that many “natural” systems are simply historical choices, and that better ones are always worth imagining.