Calendar

Calendar – “(from Latin calendar – a debt book in which the upcoming dates were indicated – “calendars” – interest payments on loans).
The calendar is designed to account for relatively long periods of time covered by the concept of “human lifespan”. The traditional units of their measurement are: “tropical year” – the period of the full cycle of the sun’s movement across the celestial sphere, as well as “average solar day”. An important place in calendars is occupied by the so-called “lunar month” – the period of the full cycle of the Moon’s movement across the celestial sphere.
The key to the calendar is the requirement that, after many thousands of years, all astronomical phenomena, such as changes in the ratio of day and night, the location of the luminaries in the firmament, etc., would occur within a strictly defined time frame. At the same time, the tropical year contains non-integers of average solar days – 365.2422 and lunar months – 12.3683 – which makes it impossible to create an accurate calendar.
During the development of European civilization, two calendars were used: Gregorian and Julian. Each of them has its drawbacks. For several decades now, but still to no avail, the idea of creating a new, more accurate calendar has been discussed, in which the duration of the months will be the same and the days of the week will be calculated according to their numerical values. As an example, Mondays fall on the 1st, 8th, 15th, 22nd and 29th of May. But despite all the benefits and convenience of this calendar, its introduction faces difficulties due to national, religious and everyday traditions.
Gregorian holidays.
In 1582, a calendar was adopted, named in honor of Pope Gregory XIII. A possible reason was the lag, which by that time had already reached 10 days from the astronomical phenomena that were characteristic of the Julian calendar. In most of Europe, this year, after October 4, October 15 came and the five-hour backlog was eliminated. According to the Gregorian calendar, as in the case of the Julian calendar, for three consecutive years it is equal to 365 days, and each subsequent leap year contains 366 days. Unlike the Julian calendar, the number of years that complete the century – 1700, 1800, etc. – included only those that have numbers starting with 400, which means 1600, 2000, 2400, etc. This allowed the Gregorian calendar to be more accurate and precise compared to the Julian calendar, which lags behind astronomical phenomena by one day in 3,300 years.
In Russia, in 1918, the Gregorian calendar was introduced as an official one. Already at this time, the lag from the Julian calendar began to exceed 14 days. As a result, they were excluded from the current 1918 year. Since now, in order to indicate the dates of historical events, the phrase “in a new style” has been used.
The name is Julian.
According to historical data, the calendar was introduced in 46 BC by Julius Caesar and was subsequently named after him – the Julian calendar. It was a calendar that included 365 days for three years in a row. Every fifth of the four rooms has 366 days at their disposal. Taking into account these circumstances, the adopted calendar lagged behind astronomical phenomena by as much as 3 days for 400 years, and then, due to the accumulation of errors, it was replaced by a more accurate Gregorian calendar. The days when the Julian calendar was adopted as the official one should not be confused with the Julian calendar.”