Calendar
A calendar (Latin: calendārium, from calends "first day of the month") is a system of measuring long periods of time. Calendars start from a date called an epoch.
Calendars predate written history, as reflected by astrological monuments such as Newgrange and Stonehenge in the British Isles, Uxmal in Mexico, and the Nebra sky disc in prehistoric Germany.
Julian calendar
The Julian calendar was developed by Julius Caesar and Augustus during classical antiquity. This calendar lasted until the modern era until the gradual adoption of the Gregorian calendar starting in the 16th century. The hesitancy to adopt the reforms was associated with anti-Catholicism.
Gregorian calendar
The Gregorian calendar is the system of timekeeping which predominates globally. Most Islamic countries record dates primarily in Gregorian terms rather than in the Islamic calendar, and East Asian countries in the historic Chinese sphere of influence continue to use the Chinese calendar only for computing religious dates. In Chinese, dates in the Gregorian calendar are referred to only by number: "Month five, weekday six, day thirty-one".
Old Style and New Style dates
In the Orthodox Russian Empire, the Julian calendar was preserved into the 20th century, at least partially because of the religious associations of the Gregorian system. This resulted in a shift of about 12 days[citation needed] between the two calendars, a difference which persisted into the eventful year 1917 and therefore caused certain dates to differ between the western and eastern systems. Thus, the February Revolution occurred in the Gregorian month of March, and the October Revolution of October 25th actually took place on what now would be called November 7. Shortly after the Bolshevik seizure of power, the RSFSR finally implemented the reform in 1918 by skipping from February 1 to February 13.
Dates recorded using the Julian calendar are now referred to as Old Style (O.S.) dates, and Gregorian dates are called New Style (N.S.).
Revolutionary calendars
French Revolutionary calendar
In the spirit of the European Enlightenment, the French bourgeois revolution encouraged critique of every previous institution, from the writings of Voltaire against the Church and American slavery to a scientific overhaul of weights, money, measurements, and even time itself. In addition to decimal time, a short-lived reform which based hours, minutes, and seconds on multiples of ten, the revolutionaries attempted to institute the French Republican (or French Revolutionary) calendar in order to replace the Christian calendar with one compatible with "the cult of reason". This calendar replaced the seven-day week of ancient Jewish origin with a ten-day week (with only one day of rest) and twelve months of 30 days each, making up the difference with leap days known as "Sansculottides". These months had brand-new faux-Latin names based on the season, such as vendémiaire for September (from vendange "vintage") and floréal for April (from fleur "flower"). Years were reckoned based on the founding of the French Republic, making 1789 "Year I", 1790 "Year II", and so on. The Republic ended on 11 Frimaire, Year XIII (2 December 1804) when Napoleon was crowned emperor, and he would abolish the calendar a year later.
The French Republican calendar is notable today mainly for its use to refer to significant developments during the revolutionary period, including but not limited to the 9th of Thermidor Year II, when Maximilien Robespierre was arrested by his enemies, and the 18th of Brumaire, Year VIII, when Napoleon first seized power and made himself First Consul. These two are the most notable uses of French Revolutionary calendar outside of histories of the French Revolution: the former lends its name to the Thermidorian Reaction which followed it, and the latter was famously referenced by Karl Marx in his work The Eighteenth Brumaire of Louis Bonaparte, which unfavorably compared Napoleon's imitative nephew with the genuine article.
The French Republican calendar was briefly revived during the iconoclastic and anti-religious Paris Commune of 1871.
Further calendar reform
Several proposals for calendar reform exist. These proliferated during the 20th century, the height of the progressive liberal ideology which predated the nihilistic postmodern era. This coincided with auxiliary language proposals such as Esperanto, spelling and language reforms, timekeeping reforms, secularization, and other proposals which were intended to dissolve national distinctions, end wars, and coordinate the flow of capital. However, many proponents of these ideas were also socialists who saw the incompatibility of the liberal idea of progress with the liberal economic order.