The Chinese calendar -which existed there already since around 2000 BC- was adopted by Japan from around the 6th century AD, together with Buddhism.
The Zodiac has an influence on the character of mankind. Each of the 12 ‘animals’ has specific characteristics. Persons born in the year of the Rat (nezumi) are charming, honest, ambitious, and have a tremendous capacity for pursuing a course to its very end. They will work hard for their goals. They are easily angered but maintain an outward show of control.
During the last century, years of the Rat were in 1912, 1924, 1936, 1948, 1960, 1972, 1984,1996 1nd 2008. In each 60 year cycle, the 12 zodiac animals are repeated 5 times, representing the 5 elements Wood, Fire, Earth, Metal and Water.
Of course it is not that simple; 60 is merely the most common denominator of 10 x 12, the ten being the 5 elements but in order to make it ten, the Japanese have adopted a big (elder) brother and small (younger) brother of each of the five stated elements. In all eastern languages, big brother and younger brother is one noun each, and not formed by a noun (brother) plus an adjective (younger or bigger [elder]) like in western languages. Actually, the year of the Rat starts on January 25, 2020 and lasts till February 12, 2021.
As the 1st animal in the Eastern zodiac, the Rat indicates the hours between 1 am and 3 am.
Best wishes to all for a splendid Year of the Rat, 2020!