The lunar calendar (農曆nóng lì) is the traditional Chinese calendar and is often used in agriculture. It is formed on the movement of the moon and the sun. Although China has adopted the Gregorian calendar（公曆 gōng lì）for offical and business occasions, but the traditional Chinese calendar is widely used to define 24 solar terms , traditional holidays ,and helps to choose a lucky day before important activities such as wedding, moving into a new house, etc.
How does the Lunar Calendar work ?
Each time the moon moves into a line with the earth and the sun , a new month begins and this is called （初一chū yī） , meaning the first day of a lunar month. When the full moon appears , it is the middle of the month. The time of a full moon cycle is a little more than 29 days, so one month has 29 or 30 days.
There are 12 or 13 months in a lunar year. The month with its first day nearest the beginning of spring (立春lì chūn， the first solar term) is the first lunar month, and on that day the Spring Festival （春節chūn jié）is held and this varies between 20th January and 20th February.
24 Solar Terms
After observing the sun's movement, ancients have found the longest day and the shortest day of a year, respectively Summer Solstice and Winter Solstice. Using these two annual events, a Chinese calendar year was divied into 24 equal parts, each forming a solar term. 24 solar terms show people's understanding of four seasons, climate and agriculture. For instance, the Beginning of Spring (立春 lì chūn) symbolizes the coming of Spring. Grain in Beard ( 芒種máng zhòng) means it is time to harvest wheat and Greater Cold ( 大寒dà hán) signifies the coldest time of a year.
Five Elements
Ancient Chinese believed the universe was composed of five elements, namely metal（金jīn), wood(木mù), water(水shuǐ), fire(火huǒ )and earth(土tǔ). Chinese like to find out their element using their birth date in lunar calendar and predict their life horoscope, like what career they are suitable for and what kind of people they are supposed to marry.
Differences between Chinese lunar calendar and Gregorian calendar
Chinese lunar calendar is calculated based on the movement of the moon and the sun, Gregorian calendar is calculated by the movement of the sun. When the earth goes around the sun for one circle, it is one year. Generally speaking, lunar calendar is 20 - 50 days later than Gregorian calendar.