Sun and Moon Astronomical Data for Chinese Calendar
|
Chinese Lunar Calendar utilizes Sun and Moon astronomical data to determine the lunar months and leap (intercalary) months. Without high precision astronomical data, the locations of Leap Months might be misplaced, which impacts the names of consecutive lunar months.
Leap Months
The difference between the Chinese 
Astronomical Calendar and
the 
Civil
Calendar is the way to assign the location of Lunar Leap Months.
In Astronomical Calendar, a Leap Month is a lunar month without a Solar Center Point in the month. A lunar month is a period of time from a new moon to the next new moon.
In Civil Calendar, a Leap Month is a lunar month without a Solar Center Point. However, as long as the new moon day and the Solar Center Point fall on the same day, the lunar month is considered having that Solar Center Point and is not a Leap Month.
For example, 1998
| UT Astronomical Calendar | China Time zone Civil Calendar | US PST Civil Calendar |
|
1998/06/21 14:03:39 Center |
1998/06/21 22:03:39 Center
|
1998/06/21 06:03:39 Center
|
|
Leap Month after 6th Lunar Month |
Leap Month after 5th Lunar Month |
Leap Month after 6th Lunar Month |
|
Lunar Month of 1998/07/23 21:44 contains the Center Point of 1998/07/23 08:56:26, because they are on the same day. |
The assignments of Leap Months for 24 different time zones are the same in the Astronomical Calendar system. The 1998 example shows the assignment of Leap Month are different between China time zone and the US Pacific time zone. Another detail example is in the page of the Leap Month in Year 2001.
Fake Leap Month
In the winter, the length of a lunar month might be longer than the length of a solar month. It's possible that a lunar month contains two Center Points. Because a lunar month steals a Center Point from the following month, there will be a month without a Center Point in one of following months. Such month missing a Center Point is called a Fake Leap Month. See the 5th rule of Chinese Lunar Calendar.
For example, 2052-2053
| UT Astronomical Calendar | China Time zone Civil Calendar |
|
2052/12/21 04:16:00 N
|
2052/12/21 12:16:00 N
|
|
Fake Leap Month in not a Leap Month. The name of Fake Leap Month is determined by the name of the Center Point in previous lunar month. |
|
The 1st lunar month of Chinese Civil Calendar in 2053 is a Fake Leap Month and removed from the Leap Month listing. The 2nd lunar month of Astronomical Calendar in 2053 is not a Leap Month, either.
For example, 1984-1985
| UT Astronomical Calendar | China Time zone Civil Calendar |
|
1984/10/24 12:09:00 N
|
1984/10/24 20:09:00 N
|
|
No Fake Leap Month in 1985 |
Leap Month in 1984 and Fake Leap Month in 1985 |
From 1645 to 2245, Only five Fake Leap Months (1680, 1700, 1719, 2053, 2072) are found in Chinese Astronomical Calendar; but 18 Fake Leap Months are found in Chinese Civil Calendar.
Double Fake Leap Months
From 1645 to 2245, it happens that two Fake Leap Months are found in a row during 2033, 2128 and 2242 in China time zone Civil Calendar.
| 2033-2034 | 2128-2129 | 2242-2243 |
|
2033/10/23 15:29:00 N
|
2128/09/24 21:03:00 N
|
2242/09/25 22:16:00 N
|
The lunar month of 2242/10/25 is a Leap Month |
The 11th and 1st lunar months are Fake Leap Months and removed from the China time zone Civil Calendar system. From 1645 to 2245, there is no Double Fake Leap Month in the Astronomical Calendar system.
Chinese New Year Day
The first lunar month of the year is the 
Tiger 
month, which contains 
Rain Water center point. Therefore the first day of the Tiger month is the Chinese New Year day.
| US PST Civil Calendar | China Time zone Civil Calendar |
|
2000/02/05 05:04:00 New Moon Time
|
2000/02/05 21:04:00 New Moon Time
|
|
The time difference between US Pacific standard time zone and China time zone is 16 hours. Therefore, more than 50% chances, the Chinese New Year days fall on different calendar days. US new moon times are always earlier than China new moon times. People in USA can celebrate Chinese New Year day on the same time with people in China when the Chinese New Year day is one day earlier than China's. It's
same to 24 |
|
The Tiger month is supposed to contain the solar Center Point Rain Water. Unfortunately, the issue of the Fake Leap Month makes some years exceptional. From 1645 to 2245, we found the Tiger month doesn't contain the Rain Water in 1681, 2053 and 2071 of Astronomical Calendar.
| UT Astronomical Calendar | Reason |
|
1680/11/21 06:38:00 New Moon
|
Two Center Points in the lunar month of 1680/11/21, which makes Chinese New Year month 1681/02/18 without the Rain Water Center Point. |
|
2052/12/21 04:16:00 New Moon
|
Two Center Points in the lunar month of 1680/11/21, which makes Chinese New Year month 2053/02/18 without the Rain Water Center Point. |
|
2071/12/21 11:48:00 New Moon
|
Two Center Points in the lunar month of 2071/12/21, which makes Chinese New Year month 2072/02/19 without the Rain Water Center Point. |
|
1718/12/22 02:27:03 C |
Chinese New Year month 1719/01/20 contains two Center Points. One of then is the Rain Water. |
From 1645 to 2245, there are nine Tiger months without the Rain Water in the lunar month in the China Civil Calendar. They are 1662, 1700, 1852, 1814, 2034, 2129, 2148, 2186 and 2243.
Winter Solstice
Before 
Shiah Dynasty (2183-1752 B.C.), the first month of the year was
defined on the 11th lunar month which contains the 
Winter Solstice Center Point. It's true that 11th lunar months
contains Winter Solstice from 1645 to 2245 in the Astronomical Calendar, but
Five 11th lunar months in the China Civil Calendar contain the Severe
Cold Center Point instead of Winter
Solstice from 1645 to 2245. They are 1813, 2185, 2033, 2128 and
2242.
| China Civil Calendar | Reason |
|
1813/09/23 19:07:56 C
|
The 9th Lunar Month 1813/10/24 contains two Center Points. Center Point Winter Solstice fall in the 10th Lunar Months of 1813/11/23. |
|
2185/11/22 10:23:00 10th New Moon 2185/11/22 05:14:00 Center
|
The 10th Lunar Month 2185/11/22 contains two Center Points. One of them is the Center Point Winter Solstice. |
The location of the Winter Solstice is not the issue for the current Chinese Lunar calendar system, because the first day of the year is not the Winter Solstice day any more.
The Pattern of 7 Leap Months in 19 Year
Some articles report the Leap Month is after 11th Lunar Month in 2033 of China Civil Calendar. But our calculation shows the Leap Month is after 7th Lunar Month in 2033.
After examining the Leap Months from 1645 to 2245 in the China Civil Calendar by gathering every 7 years in a group, we find
If you follow the pattern of 7 Leap Months in 19 year, it makes much more sense to assign Leap Month after 7th Lunar Month in 2033 of Chinese Civil Calendar.
| UT Astronomical Calendar | China Time zone Civil Calendar |
|
1998/07/23 13:44:00 Leap 06 1
|
1998/06/24 11:51:00 Leap 05 1
2033/12/21 21:47:08 C <- Double Center |
|
No Fake Leap month found |
Leap Months should remove after Double-Center-Point months |
There is no discussion issue in the Astronomical Calendar in 2033, because there is no Double-Center-Point Month or Fake Leap Month in the system.
Conclusion
Because it's possible the length of a lunar month is longer than a solar time, then there is a chance of that a lunar month owns two solar Center Points. This issue generates the problems of Fake Leap Month and the names of lunar months between the Double-Center-Point Lunar Month and the Fake Leap Month.
From all the previous examples, we can realize that the Chinese Astronomical Calendar generate much less trouble from the Fake Leap Month. The Leap Month assignments of 24 time zones are the same in the Astronomical Calendar system. Certainly, Chinese Astronomical Calendar is the easiest and best solution for next generation of the Chinese Calendar.
For all the applications in Chinese astrology, we should use the Astronomical Calendar simply because it's accuracy. We can keep the China Civil Calendar for the Chinese government. When doing the software programming, we can give users the choice for selecting the Astronomical Calendar or China Civil Calendar.
Because the difficulty of Leap Month assignment, there is no simple formula
for the software programming. Also, without high precision Sun and Moon
astronomical data, the assignment of Leap Month might be wrong. This is very
crucial for the application in the Chinese astrology 
Dipper system, which uses the lunar month to determine the astrology birth
chart.
We already generate the high precision Sun and Moon astronomical data in different list formats for people. Those Astronomical data can be easily applied on different types of applications.
Sun and Moon Astronomical Data For Software Programming
solar
segment times. The days of solar segment might fall on
the different days among different time zones.
Home of Chinese Lunar Calendar