Few thousands years ago, Chinese decided to go pictorial, instead of phonetic, for its language. It turns out to be quite a unique decision. Chinese calendar is similarly unique.

It is almost completely astronomical. Almost all important dates can be derived, or computed, from astronomical events. Dershowitz and Reingold published the algorithms in their remarkable book. Calendrical Calculations (ISBN 0521564131, 1997). They wrote all code in Scheme, my favorite computer language.

(Scheme is a beautiful and pure computer language. There is one and only one way to abstract -- by defining a function. Language execution is defined mathematically, without compromising what can be implemented efficiently. I believe all software engineers must have few years of Scheme programming experience.)

Chinese farmers use solar calendar. Starting with winter solstice, the solar year is divided into 24 periods, marked by major and minor solar events alternatively. Agricultural activities follow these calendrical markers. The rest of the society plans their lives according to the moon, an easily observable object. If it is the new moon, go to the worshipping place. When full moon comes, go to the market. And so on..

They come together at New Year, generally defined as the 2nd new moon after the winter solstice. Since 12 lunar months are shorter than a solar year. Chinese adds a months to once in a about every three years. That will be a leap year.

Years are numbered in cycles of 60. You can think a Chinese "century" is 60 years. Instead of numbers, Chinese name these 60 with two counters: one in the cycle of 10 and the other 12. The former is called the "heavenly" counter (天干, TianGan） and the latter "earthly" （地支, DiZhi）. The earthly counter is actually 12 animals.

Chinese actually use the same system to count months, days, and hours too. One can therefore describe any two hour period with 8 characters: 2 each for year, month, day, and hour. These 8 characters are known to have magical power that determines one's fate. I studied that for few years. But that's another blog entry in the future.

On January 29th, obviously a new moon, the year 丙戌 (BingXu) starts. This happens to be year 4703 from the Chinese epoch.