Seasonal year

The seasonal year is the time between successive recurrences of a seasonal event such as the flooding of a river, the migration of a species of bird, or the flowering of a species of plant.

The need for farmers to predict seasonal events led to the development of calendars. However, the variability from year to year of seasonal events (due to climate change or just random variation) makes the seasonal year very hard to measure. This means that calendars are based on astronomical years (which are regular enough to be easily measured) as surrogates for the seasonal year. For example, the ancient Egyptians used the heliacal rising of Sirius to predict the flooding of the Nile.

A study of temperature records over the past 300 years suggests that the seasonal year is governed by the anomalistic year rather than the tropical year.

This suggestion is surprising because the seasons have been thought to be governed by the tilt of the Earth's axis (see Effect of sun angle on climate). The two types of years differ by a mere 4 days over 300 years, so Thompson's result may not be significant. However, the result is not unreasonable. The seasons can be considered to be an oscillating system driven by two inputs with slightly different frequencies: the total input of energy from the sun varies with the anomalistic year, while the distribution of this energy between the hemispheres varies with the tropical year. In other physical situations, oscillating systems driven by two similar frequencies can latch onto either one. One point that must be considered is that the oscillation arising from the tilt of the axis is much greater than that arising from the distance of the sun.

New Year

New Year is the time at which a new calendar year begins and the calendar's year count increments by one. Many cultures celebrate the event in some manner. The New Year of the Gregorian calendar, today mostly in use, falls on 1 January (New Year's Day), as was the case both in the old Roman calendar (at least after about 713 BCE) and in the Julian calendar that succeeded it. The order of months was January to December in the Old Roman calendar during the reign of King Numa Pompilius in about 700 BCE, according to Plutarch and Macrobius, and has been in continuous use since that time. Many countries, such as the Czech Republic, Italy, Spain, the UK, and the United States, mark 1 January as a national holiday.

During the Middle Ages in western Europe, while the Julian calendar was still in use, authorities moved New Year's Day variously, depending upon locale, to one of several other days, among them: 1 March, 25 March, Easter, 1 September, and 25 December. These New Year's Day changes generally reverted to using January 1 before or during the various local adoptions of the Gregorian calendar, beginning in 1582. The change from March 25 – Lady Day, one of the four quarter days – to January 1 took place in Scotland in 1600, before the ascension of James VI of Scotland to the throne of England in 1603 and well before the formation of the Kingdom of Great Britain in 1707. In England and Wales (and in all British dominions, including Britain's American colonies), 1751 began on March 25 and lasted 282 days, and 1752 began on January 1. For more information about the changeover from the Julian calendar to the Gregorian calendar and the effect on the dating of historical events etc., see Old Style and New Style dates.

Chinese astrology

Chinese astrology is based on the traditional astronomy and calendars. The development of Chinese astrology is tied to that of astronomy, which came to flourish during the Han Dynasty (2nd century BC to 2nd century AD).

Chinese astrology has a close relation with Chinese philosophy (theory of the three harmony, heaven, earth and water) and uses the principles of yin and yang and concepts that are not found in Western astrology, such as the wu xing teachings, the 10 Celestial stems, the 12 Earthly Branches, the lunisolar calendar (moon calendar and sun calendar), and the time calculation after year, month, day and shichen (時辰).

Background

Chinese astrology was elaborated during the Zhou dynasty (1046–256 BC) and flourished during the Han Dynasty (2nd century BC to 2nd century AD). During the Han period, the familiar elements of traditional Chinese culture—the Yin-Yang philosophy, the theory of the 5 elements, the concepts of Heaven and Earth, and Confucian morality—were brought together to formalize the philosophical principles of Chinese medicine and divination, astrology and alchemy.