The word “calendar” came from ancient Rome. It was derived from the word for debtor’s account books, where the interest was documented monthly. There were three types of calendars: solar, lunar, and lunisolar. The first type was the most common one: it was based on the movement of the Sun, making it possible to establish the day and year.

One of the first to use the calendar was the ancient people of Sumer. Later, Babylonian priests determined that the year consisted of 365.6 days.

In 46 BC, Gaius Julius Caesar introduced the Julian calendar (also called Old Style calendar). This was necessary since the existing Roman calendar was very different from the solar one: at that time, it was already 90 days ahead. The new calendar was based on the annual motion of the Sun through the twelve constellations making up the zodiac. According to the emperor’s decree, the year began on January 1.

The second significant reform was introduced by Pope Gregory XIII in 1582 — a new calendar called Gregorian (also known as New Style calendar). The changes were dictated by the fact that the day of the vernal equinox, which is very important for setting the dates of religious holidays, was gradually moving throughout the years, and as a result came earlier and earlier every time.

Up until Peter I issued the decree introducing a new calendar, Russians had followed a calendar dated from the birth of Adam, which, according to Christian teaching, took place in 5506 BC: they celebrated the beginning of a new year in September, after harvesting, or in March, on the day of the vernal equinox.

The emperor’s decree aimed at keeping Russian chronology with the European one and established January 1 as New Year’s Day. Until October 1917, Russia lived according to the Julian calendar, falling thirteen days behind the calendar used by European countries. When the Bolsheviks came to power, they changed the calendar. On February 1, 1918, a decree was issued declaring that day to be February 14.

The revolutionaries were dangerously close to completely reforming the Russian calendar according to their ideology. In the 1930s, a proposition was made to introduce “five-day periods” instead of weeks. And in 1939, the League of Militant Atheists suggested naming the months from January to December the following way: Lenin, Marx, Revolution, Sverdlov, May (this one was approved), Soviet Constitution, Harvest, Peace, Comintern, Engels, Great Revolution, and Stalin. Fortunately, the proposition was rejected.