Chinese calendar, a lunisolar calendar阴阳合历, is formed on the movement of the moon. It defines界定 Chinese 24 solar terms节气, traditional holidays and helps to choose a lucky day选定良辰吉日 before important activities such as 

marriage proposal订婚, 
wedding结婚, 
praying for pregnancy求子,
traveling出行.

闰年
Leap Years

The Chinese calendar features 12 months有12个月份. However, an extra month is inserted in the calendar when a leap year occurs每逢闰年时要添加一个月. Therefore, leap years in the Chinese calendar have 13 months, unlike leap years in the Gregorian calendar公历 in which an extra day is included添加一天. A leap month is added to 添加the Chinese calendar approximately every three years (7 times in 19 years). The name of the leap month is the same as the previous lunar month闰月的名称与之前的阴历月份名称相同. A leap year in the Chinese calendar does not necessarily不一定 fall at the same time a leap year occurs in the Gregorian calendar.

The Chinese calendar's origins can be traced as far back as追溯到 the 14th century BCE. The Shang oracle bones甲骨文 give evidence of a lunisolar calendar which has been much modified but persists to this day 延续至今. It is believed that the Emperor Huangdi (Huang Ti or Huang Di)黄帝 introduced the calendar between 3000 and 2600 BCE, or around 2637 BCE.

黄历，又称老黄历、皇历，是在中国农历基础上产生出来的，带有每日吉凶宜忌的一种万年历。黄历相传是由轩辕黄帝创制，故称为黄历。黄历主要内容为二十四节气，每天的宜忌、干支、值神、星宿、月相、吉神凶煞等。

黄历是古时帝王遵循的一个行为规范的书籍，并由钦天监计算颁订，因此也称皇历；这里面不但包括了天文气象、时令季节而且还包含了人民在日常生活中要遵守的一些禁忌，其内容指导中国劳动农民耕种时机，故又称农民历；中国民间俗称为通书；但因通书的“书”字跟“输”字同音，因避忌故又名通胜。

在现代，黄历的主要内容包括：公历、农历和干支历三套历法，二十四节气与礼拜天（星期）、宜忌、冲煞、方位、流年、太岁、三元九运、玄空九星等等。

China resisted the Gregorian calendar抵制使用公历 until 1912 but it was not widely used throughout the country until the Communist victory in 1949. This widespread change occurred on October 1, 1949, when Mao Zedong, who led the People's Republic of China, ordered that the year should be in accord with保持一致 the Gregorian calendar.

天干地支
Heavenly Stems & Earthly Branches

Although China has adopted the Gregorian calendar in common with most other countries in the world for official and business purposes, the traditional Chinese calendar continues to define the dates of festivals界定节日 and is used for horoscopes占卜. The calendar has a very long history going back to the Xia追溯到 (21st century BC - 16th century BC) and Shang Dynasty (16th century BC - 11th century BC). It is based on a unique combination of astronomy and geography through observation and exploration. It is also referred to as the Lunar, Yin, Xia or the old Chinese calendar.阴历、夏历或老黄历

Following its creation in the Xia Dynasty, succeeding reigns continued to use the calendar but modified it from time to time. The Han Dynasty rulers instituted the Taichu calendar, while during Tang Dynasty the Huangji calendar was introduced and it was adopted by Japan, Korea and Vietnam. With the founding of the Republic of China in 1912, the Gregorian calendar was brought into use开始使用公历. Although ethnic groups such as Tibet and Dai have their own calendars, in essence本质上来讲 they resemble that of the Han people与汉族的很相似. Islam reckons its own religion festivals according to the Islamic Calendar.

The calendar has links with natural sciences such as agriculture and astronomy天文学, solar terms节气, the four seasons and traditional festivals such as the Spring Festival. There are links also with the 'Five Elements'五行 of which the ancient Chinese believed the physical universe物质世界 to be composed namely, metal, wood, water, fire and earth金木水火土. Finally, of course, is Chinese Zodiac属相 - the symbolic animals生肖 associated with each year on a 12-year cycle.

Rules for Calculation

Each time the moon moves into line with the earth and the sun a new month begins and this is called 'Chu Yi'初一 or 'Shuo Ri' (the first day of a lunar month)朔日. The longest day of a year or Summer Solstice夏至 falls on在哪一天 the 21st or 22nd of June, and the shortest day is the Winter Solstice冬至 on either December 21, 22, or 23. Using these two annual events the year was divided into in 24 equal parts, each forming the 24 solar terms. The month with its first day nearest the Beginning of Spring (the first solar term)立春 is the first lunar month, and on that day the Spring Festival is held春节 and this varies不固定，介于之间 between January 20th and February 20th.

In China, there are public holidays公休假日on 7 legal festivals法定节日 in a year, namely New Year's Day元旦, Chinese New Year (Spring Festival)春节, Qingming Festival清明节, May Day五一劳动节, Dragon Boat Festival端午节, Mid-Autumn Festival端午节, and National Day国庆节.

五四青年节Youth Day
六一儿童节 Children's Day
八一建军节Army Day of the Chinese People's Liberation Army
有半天假Women have half day off on Women's Day.

Young people over 14 years of age have a half day off on Youth Day. Children under 14 years old have a day off on Children's Day.

现役军人Active members of the army have a half-day off on Army Day.
植树节Arbor Day
教师节Teachers' Day

属相延伸阅读
Chinese Zodiac Origins — Why 12 Animals

The 12 animals were chosen deliberately, after many revisions. The zodiac animals are either closely related to ancient Chinese people’s daily lives, or have lucky meanings.
The ox, horse, goat, rooster, pig, and dog are six of the main domestic animals raised by Chinese people.六大家畜 The other six animals: rat, tiger, rabbit, dragon, snake, and monkey are all loved by the Chinese people. 喜爱的动物

Why the 12 Zodiac Animals Are in That Order

The 12 Chinese Zodiac animals are in a fixed order according to Chinese Yin and Yang Theory and perceived attributes人们认为它们具有的特性.
The yin or the yang of the animals is defined based on the odd or even number 奇数和偶数of their claws (or toes, hoofs)爪子、脚趾或蹄子. The animals are then arranged in an alternating (complementary) yin-yang sequence.奇、偶数交替排序
Usually an animal has the same number of claws on its front and rear legs前后腿. However, the rat has four toes on its fore legs and five on its hind legs.老鼠很特殊，前腿有四个脚趾，后退有五个脚趾

As the old saying goes, “a thing is valued in proportion to its rarity”物以稀为贵, so the Rat ranks first of the 12 zodiac animals因此老鼠列12生肖之首. It uniquely combines the attributes of odd (yang) and even (yin). 4+5=9, and yang is dominant, so the Rat is classified as odd (yang) overall. 鼠总体上被归为“阳”
Each animal has symbolic meanings象征意义 given to it by the ancient Chinese. These animal attributes动物特性 come in six contrasting pairs分为对比鲜明的六组 that must be harmonized必须进行调和, like yin and yang, and are the primary factor governing the order of the zodiac是属相排序的主要因素.

Rat    Wisdom    without industriousness leads to triviality.
Ox    Industriousness    Industriousness without wisdom leads to futility. 
第一组是老鼠和牛，老鼠代表智慧，牛代表勤奋。智慧和勤奋一定要紧紧结合在一起。如果光有智慧，不勤奋，那就变成小聪明：而光是勤奋，不动脑筋，那就变成愚蠢。这两者一定要结合。这是祖先对我们第一组的期望和要求，也是最重要的一组。”

Tiger    Valor    Valor without caution leads to recklessness.
Rabbit    Caution    Caution without valor leads to cowardice.
第二组是老虎和兔子。老虎代表勇猛，兔子代表谨慎。勇猛和谨慎一定要紧紧结合在一起才能作到胆大心细。如果勇猛离开了谨慎，就变成了鲁莽，而没了勇猛，就变成了胆怯。这一组也非常重要，所以，放在第二位置上。通过这一组，我也可以告诉你们这些西方人，当我们炎黄人表现出谨慎的时候，千万不要以为炎黄人没有勇敢的一面

Dragon    Strength    Strength without flexibility leads to fracture.
Snake    Flexibility    Flexibility without strength leads to compromise.
第三组是龙和蛇，代表刚猛，蛇代表柔韧。所谓刚者易折，太刚了容易折断，但是，如果只有柔的一面就易失去主见，所以，刚柔并济是我们的祖训。”

Horse    Forging ahead    Forging ahead without unity leads to abandonment.
Goat    Unity    Unity without forging ahead leads to stagnation.
马和羊，马代表勇往直前，羊代表和顺。如果一个人只顾自己直奔目标，不顾及周围环境，必然会和周围不断磕碰，最后不见得能达到目标。但是，一个人光顾及和顺，他可能连方向都没有了。所以，勇往直前的秉性，一定要和和顺紧紧结合在一起，这是祖先对我们的第四组期望

Monkey    Changeability    Changeability without being constant leads to foolishness.
Rooster    Being constant    Being constant without changeability leads to woodenness.
猴子和鸡。猴子代表灵活，鸡定时打鸣，代表恒定。灵活和恒定一定要紧紧结合在一起。如果你光灵活，没有恒定，再好的政策也得不到收获。一方面具有稳定性，保持整体和谐和秩序，另一方面又能在变通中前进，这才是最根本的要旨。”

Dog    Fidelity    Fidelity without amiability leads to rejection.
Pig    Amiability    Amiability without fidelity leads to immorality.
狗和猪。狗代表忠诚，猪代表随和。如果一个人太忠诚，不懂得随和，就会排斥他人。反过来，一个人太随和，没有忠诚，这个人就失去原则。无论是对一个民族的忠诚，还是对自己理想的忠诚，一定要与随和紧紧结合在一起，这样才容易保持内心深处的平衡。”