Why is there Chinese New Year

Chinese New Year (Simplified Chinese: 春节, or 农历新年, Traditional Chinese: 春節, or 農曆新年; pinyin: chūnjié, or nónglì xīnnián), also known as the Lunar New Year or the Spring Festival is the most important of the traditional Chinese holidays. It consists of a period of celebrations, starting on New Year's Day, celebrated on the first day of the first month of the Chinese calendar. This is the day of the second new moon after the winter solstice, unless there is an intercalary eleventh or twelfth month in the lead-up to the New Year. In such a case, the New Year falls on the day of the third new moon after the solstice. (The next time this occurs is in 2033.) The Chinese New Year period ends with the Lantern Festival, on the fifteenth day of the festival.

According to legend, the beginning of the year began with month 1 during the Xia Dynasty, month 12 during the Shang Dynasty, and month 11 during the Zhou Dynasty, but intercalary months were added after month 12 during both the Shang Dynasty according to surviving oracle bones and the Zhou Dynasty according to Sima Qian. The first Emperor of China Qin Shi Huang changed the beginning of the year to month 10 in 221 BC. Whether the New Year was celebrated at the beginning of these months or at the beginning of month 1 or both is unknown. In 104 BC, Emperor Wu established month 1 as the beginning of the year where it remains.

According to legend, in ancient China, Nian ("Nyan"), a man-eating predatory beast from the mountains, could infiltrate houses silently. The Chinese were always very scared of this monster. The Chinese later learned that Nian was sensitive to loud noises and the color red, and so they scared it away with explosions, fireworks and the liberal use of the color red. So "GuoNian" actually means "Passover the Nian". These customs led to the first New Year celebrations.

Ancient Chinese observed the orbit of the moon, the intervals and pattern between its repetitive cycle, its position and its relationship with the weather and derived the Chinese date calculating system called the lunar calender. Whereas, ancient Western astronomers observed the orbit of the sun (of course now we know its actually the orbit of the earth aound the sun) to come up with a date calculating system. That's why in Chinese its called 陽曆.

Although within some never changing natural laws, the years somehow compensate in a way that the western calender and lunar calender will not drag apart too far, they do differ in the day and month calculations. It is therefore Chinese has a different New Year Day due to a the use of a different calender.