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.