Decimal calendar

The ancient Egyptian calendar consisted of twelve months, each divided into three weeks of ten days, with five intercalary days.^[1]

The original Roman calendar consisted of ten months; however, the calendar year only lasted 304 days, with 61 days during winter not assigned to any month.^[2] The months of Ianuarius and Februarius were added to the calendar by Numa Pompilius in 700 BCE.^[2]

The French Republican Calendar was introduced (along with decimal time) in 1793, and was similar to the ancient Egyptian calendar.^[3] It consisted of twelve months, each divided into three décades of ten days, with five or six intercalary days called sansculottides.^[3] The calendar was abolished by Napoleon on January 1, 1806.^[3]

The modern Gregorian calendar does not use decimal units of time; however, several proposed calendar systems do. None of these have achieved widespread use.^{[example needed]}

• Decimal time