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As a child, I visited my grandmother weekly and one thing that caught my attention was a calendar with which I was not familiar. Compared to the calendar I was accustomed to, this one had more ‘annotations’ and peculiar symbols. It looked something like this:

This calendar has many names; it is known as the Rural Calendar/Former Calendar/Traditional Calendar/Lunar Calendar. It is a lunisolar calendar (a calendar whose date indicates both the moon phase and the time of the solar year).

The Chinese calendar is based on observations of astronomical cycles, whereas our Gregorian calendar uses set dates that approximate astronomical cycles. The Gregorian calendar is a solar calendar because it is based on the Earth’s revolution of the Sun and the progression of seasons. Consequently, every Gregorian year is the same (except in the case of leap years).

On the other hand, the Chinese calendar tracks time according to the cycle of the moon’s phases as well as the progress of the Sun. Each month begins with the occurrence of a new moon. This results in the Chinese calendar sometimes having an extra month included in the year, and from one year to the next, a variable number of days to make up the length of a year.

Since the months of the Chinese calendar are derived from the lunar cycle, which lasts 29.53 days on average, Its months are either 29 or 30 days long. Like the Western Calendar, the Chinese calendar’s ordinary year has 12 months. However, there will be a leap month every leap year (occurs every two or three years). The ordinary year in the Chinese calendar runs between 353 and 355 days, while a leap year has between 383 and 385 days. The system of having leap months helps ensure that the average duration of a year in the Chinese calendar is reasonably close to that of a solar year.

Unlike some lunisolar calendars, the Chinese calendar does not mark its years chronologically. Rather, the Chinese calendar names its years with two components. The first component denotes an element (e.g. metal, fire, or earth), while the second component denotes an animal (e.g. dragon, ox, monkey). For example, 2019 is the year of the Earth Pig, and it lasts from 5 February 2019 to 24 January 2020. As there are five elements and twelve animals, it follows that there are 60 different combinations (i.e. the next Earth Pig year will occur in 60 years). The following paragraph is a near-direct quote from reference [4]:

Also named the sexagenary cycle or the stem-branch cycle, the Chinese 60-year calendar cycle is based on the combinations of a cycle of ten heavenly stems and twelve earthly branches, as espoused by traditional Chinese myths. Each year is named by a pair of one stem and one branch. The Year of Jia Zi (Jia from the heavenly stems and Zi from the earthly branches) is the beginning of the sexagenary cycle. The next Jia Zi Year will come 60 years later. Jia Zi has had a figurative meaning a full lifespan in ancient times (cf ‘threescore years and ten’ in the Bible (Psalm 90:10)). People would be obviously blessed if they can meet the second Jia Zi in life. Therefore, a 60-year cycle is also called a Jia Zi.

You might be wondering: in combinations, why use a pair of one stem instead of not using a pair of one stem (i.e. a lone stem; one of the ten stems)? With 10 stems and 12 branches, shouldn’t there be 120 combinations? Apparently, the pair comes from the fact that for each of the five elements, there is a ‘yin’ and a ‘yang’. They go together and are always paired up. Hence, we have 60 combinations instead of 120.

Fun fact: Singapore’s prime minister, Mr Lee Hsien Loong, was named with a ‘dragon’ character in his name probably because he was born in the year of the dragon (1952)!

Blessed Lunar New Year to all!

Yours faithfully,
Nicholas Loh
3 February 2019

References
1. ‘Why are there so many different calendars?’ https://www.youtube.com/watch?v=DaLsuZRj9wg
2. https://en.wikipedia.org/wiki/Chinese_calendar
3. https://www.yourchineseastrology.com/calendar/2019/
4. https://www.travelchinaguide.com/intro/astrology/60year-cycle.htm
5. http://www.kiasubride.com/wp-content/uploads/2013/01/calendar.jpg