The Chinese calendar dates back centuries before the Julian calendar that we use today. It measures time based on the the astronomical movements of the Sun, Moon and stars, and is highly accurate.
The Chinese New Year is now popularly known as the Spring Festival because it starts from the Begining of Spring (the first of the twenty-four terms in coodination with the changes of Nature). Its origin is too old to be traced.
The word Nian, which in modern Chinese solely means "year", was originally the name of a monster beast that started to prey on people the night before the beginning of a new year.
The term "Guo Nian", which may mean "Survive the Nian" becomes today "Celebrate the (New) Year" as the word "guo" in Chinese having both the meaning of "pass-over" and "observe". The custom of putting up red paper and firing fire-crackers to scare away Nian should it have a chance to run loose is still around.