What is a year?
The year is a certain unit of time, it is equal to the period of rotation of the planet around the sun. On average, the duration of a year is 12 months (52 weeks plus a day or two). What is the year, they know almost everything. But many people do not know that there are several types of years: astronomical years, which, in turn, are divided into tropical, sidereal and anomalistic years; as well as calendar years.
- Gregorian calendar (365 days - non-leap year; 366 days - leap year).
- Julian calendar (365 days - non-leap year; 366 days - leap year).
- Islamic calendar (365 days - non-leap year; 366 days - leap year).
- The Jewish calendar (353, 354, 355 days - a common year; 383, 384, 385 days - a leap year).
Duration of the year (average values):
- 366.62 days - draconic year. During this time, the Sun returns to the same node of the Moon's orbit.
- 353, 354, 355 days are non-leap years in the lunisolar calendar.
- 354.37 days - the duration of the year in the lunar calendar.
- 365.2 days is a leap year in the solar calendar.
- 365.2 days - tropical year.
- 365.2 days — the new calendar from Julia
- 365.2 days - the Iranian calendar (developed by Omar Khayyamam).
- 365.2424 days - the interval between the spring equinoxes.
- 365,243 days - year in the Gregorian calendar.
- 365.25 days - a year in the Julian calendar.
- 365.2564 days - star (sidereal) year.
- 365.257 days - in the gaussian year.
- 365.26 days - in the anomalistic year.
- 366 days is a leap year in the solar calendars.
- 383, 384, 385 days - leap years in the lunisolar calendar.
- 383.9 days - leap years in other types of lunar-solar calendars.
Earth day, that is one day, is 86,400 seconds. They are defined as follows: 24 * 60 * 60.
Why is there 12 months in a year?
In 46 BC Julius Caesar decided to reform the calendar, which then consisted of 10 months. The first month was March. But according to the advice of the Egyptian astronomer Sozigen, another 2 months were added (January and February). The beginning of the year, Julius Caesar also changed to January.