Coptic calendar Roman Emperor Augustus imposed the Decree upon Egypt as its official calendar (although it was unsynchronized with the newly introduced Julian calendar which had erroneously been intercalating leap days every third year due to a misinterpration of the leap year rule so as to apply inclusive counting). To distinguish it from the Ancient Egyptian calendar, which remained in use by some astronomers until medieval times, this reformed calendar is known as the Coptic calendar. Its years and months coincide with those of the Ethiopian calendar but have different numbers and names. The Coptic year is the extension of the ancient
Decimal calendar Decimal calendar A decimal calendar is a calendar which includes units of time based on the decimal system. 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). The months of Ianuarius and Februarius were added to the calendar by Numa Pompilius in 700 BC. The ancient Egyptian calendar consisted of twelve months, each divided into three weeks of ten days, with five intercalary days. The French Republican Calendar was introduced (along with decimal time) in 1793, and was similar to the ancient Egyptian