Dear Friends,
image from www.dsexls.com / tupian.hudong.com
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pj asked why her/his 2nd Lunar-Month leap-Month birthday seems to occur so rarely that she/he is getting impatient. Here’s a similar reply to pj earlier, thought it might be interesting to others too.
As per posting The 5 Cows in the Years of Ox, me which one ?, the Chinese calendar year is based on 2 rotating cycles, i.e. the 天干 (Tian-gan) and the 地支 (Di-zhi) cycles, combining to form a 60-year cycle.
Chinese calendar is actually Lunisolar, i.e. it reflects the movement of the Moon around the Sun as well as that of the Earth around the Sun.
For the Lunar calendar, each Lunar Month is either 29 or 30 days (Moon’s orbit is about 29.5 days), so a normal year will only have 354 or 355 days, short of the 365.25 days of the Earth’s orbit around the Sun.
The Solar calendar, represented by 24 节气 (”jie-qi”) was addressed in posting Revision : 4 Seasons and 24 Jieqi (节气).
24 jie-qi is a very accurate system as markers of the position of the Earth vs the Sun, important for the agriculture, it is therefore also known as 农历 (”nong li”, “agrarian calendar”).
To address the gap between the Lunar and the Solar calendars, there are 2 adjustments :
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Leap-year (闰年) : within every 30-year cycle, there are 11 years where an additional day is added to the 12th Lunar Month, (with a 30-day 12th Month and a 355-day year). This is the strict definition of “Leap-year” 闰年,
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Leap-Month (闰月) : every 3 years there is a Leap-Month, every 5-yrs 2 leap-Months and every 19-yrs 7 leap-Months. 19 years is a complete cycle and it will corresponds to the Gregorian calendar exactly.
The 24 Jie-qi, each of about 15 days, is further divided into 2 groups, called “节气” (jie-qi) and “中气” (zhong-qi). (note the use of the same word Jie-qi).
If we numbered the 24 Jie-qi as 1,2,3,4,5,….,24, then the Odd numbered jie-qi is called “节气” and the Even-numbered jie-qi called “中气”.
冬至 (”dong zhi”, Winter Solstice) is another important marker in Chinese Calendar, it must occured in the 11th Month.
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When there are 13 New Moons between the 1st day of 11th Month to the 1st day of the 11th Month the following year (called 岁, “sui”), that will be the leap-Month year and a leap-Month inserted within the 13 “moons” period.
In a leap-Month year, the first month that does not have a complete “中气” (zhong-qi) within the 岁, (“sui”) period will have a leap-month immediately after it, called 闰月 (”run yue”, leap month), so if it is 5th Month, it is simply called 闰五月.
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The length of each jie-qi is not constant at 15 days because the orbit of the Earth around the Sun is not a perfect circle with Sun in the middle, it is elliptical with 夏至 (“xiazhi”, Summer Solstice) being furthest between the two. Therefore those jie-qi’s closer to 夏至 (before and after) will be longer too with 16 days.
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It is therefore more likely to see a “zhong-qi” straddling over two Lunar months (i.e. incomplete zhong-qi period in the month) around Xiazhi, making the Leap-Month more likely to occur in the 3rd, 4th, 5th, 6th and 7th Lunar Month.
2nd Lunar Month is quite far away from the 5th Lunar Month (when xiazhi usually occurs), therefore it is more rare leap-Month.
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Therefore congrats to pj for being borned in a rare leap-Month year !
image from www.eumetsat.int/Home
Digression :
There is a difference between 岁 (”sui”) and 年 (”nian”).
岁 (”sui”) referes to the time period between 2 consecutive Dong-zhi, whereas
年 (”nian”) refers to the time period between 2 consecutive Chun-jie.
Separately, cycles of time has many layers, in Chinese system :
十九岁为一章。 (19 sui’s is 1 zhang),
四章为一蔀，七十六岁。(4 zhang’s is 1 bu, 76 sui’s),
二十蔀为一遂，遂千五百二十岁。(20 bu’s is 1 sui, 1,520 sui’s)
三遂为一首，首四千五百六十岁。( 3 sui’s is 1 shou, 4,560 sui’s)
七首为一极，极三万一千九百二十岁。(7 shou’s is 1 ji, 31,920 sui’s)
What happen after 1 ji the biggest cycle ?
All things are destroyed and a new cycle of life begins.
As for the Buddhism world, time frame takes on a different meanning :
1 regular kalpa = 16 million years,
1 small kalpa = 1,000 regular kalpas,
1 medium kalpa = 20 small kalpa = 320 billion years,
1 great kalpa = 4 medium kalpa = 1.28 trillion years
In Buddhism, it is about space-time frame, Not time in modern sense.
Congrats if you have managed to read until this line from the beginning.
It is just a very simple idea with 2 overlapping calendar systems, making it seem complicated superficially, though some of the hidden concepts are indeed thought provoking.
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Filed under: All, Cosmic Forces, Nature
