Instrument 09 / Base ten

Decimal day

A decimal day has ten hours. Each hour has one hundred minutes, and each minute has one hundred seconds. Noon is 5:00:00.

Why this clock exists

France made decimal time official in 1793: ten hours in a day, one hundred minutes in an hour, and one hundred seconds in a minute. The Science Museum notes that the experiment was later abandoned. This dial keeps the proposal alive without asking anyone to adopt it. Its neat fractions reveal that today's familiar divisions are durable conventions, not the only imaginable structure for a day.

Science Museum decimal watch