According to Chinese Lunar calendar, the Chinese New Year Day is the new moon day of the first lunar month. The first lunar month is the second lunar month after the lunar month (11th lunar month) contains Winter Solstice, which is around December 23 in Gregorian calendar (western calendar). As a result, Chinese New Year Day might fall in the second half of January or the first half of February.

Chinese calendar combines lunar, solar and color-animal (Stem-Branch) counting systems. The lunar counting system mainly is to count the lunar month. The solar counting system is to count the year and solar month for agriculture activities. The color animal is to count the every single solar day. At the beginning color animal counts only for the day. Later, Five Element scholars applied color animals on Year and Month cycles.

There are 12 animals, which are Rat ,Cow ,Tiger ,Rabbit ,Dragon ,Snake ,Horse ,Sheep ,Monkey ,Chicken, Dog, Pig, in the counting system. The Chinese calendar needs to assign a unique animal name for each day inside the lunar month. sometimes, Chinese Lunar Calendar needs to add an extra lunar monthin the cycle to match the speed of the solar cycle. For example, Year 2006, Chinese calendar has two 7th lunar months. A lunar month contains 29 or 30 days. Therefore, Chinese calendar needs 60 different animal names to make every single day unique for the case of leap lunar month.