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.  

Astronomical and Civil 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
1998/06/24 03:51:00 N
1998/07/23 00:56:26 C
1998/07/23 13:44:00 New Moon
1998/08/22 02:04:00 New Moon

1998/08/23 07:59:59 C
1998/09/20 17:02:00 N

1998/06/21 22:03:39 Center
1998/06/24 11:51:00 New Moon
1998/07/23 21:44:00 New Moon

1998/07/23 08:56:26 Center
1998/08/22 10:04:00 N
1998/08/23 15:59:59 C
1998/09/21 01:02:00 N

1998/06/21 06:03:39 Center
1998/06/23 19:51:00 N
1998/07/22 16:56:26 C
1998/07/23 05:44:00 New Moon
1998/08/21 18:04:00 New Moon

1998/08/22 23:59:59 C
1998/09/20 09:02:00 N

Leap Month after 6th Lunar Month
1998/07/23 13:44 

Leap Month after 5th Lunar Month
1998/06/24 11:51

Leap Month after 6th Lunar Month
1998/07/23 05:44 

 

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 Chinese Lunar Leap Months

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 04:18:32 Center
2053/01/19 15:00:35 Center

2053/01/19 23:13:00 N
2053/02/18 05:03:15 C
2053/02/18 16:32:00 N
2053/03/20 03:48:44 C
2053/03/20 07:12:00 New Moon (Fake Leap Month)
2053/04/18 18:49:00 New Moon

2053/04/19 14:31:37 C

2052/12/21 12:16:00 N
2052/12/21 12:18:32 Center
2053/01/19 23:00:35 Center

2053/01/20 07:13:00 N
2053/02/18 13:03:15 C
2053/02/19 00:32:00 New Moon (Fake Leap Month)
2053/03/20 15:12:00 New Moon

2053/03/20 11:48:44 C
2053/04/19 02:49:00 N
2053/04/19 22:31:37 C

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
1984/11/22 03:11:33 C
1984/11/22 22:57:00 N
1984/12/21 16:23:44 C
1984/12/22 11:47:00 N
1985/01/20 02:58:29 C
1985/01/21 02:29:00 N
1985/02/18 17:08:19 C
1985/02/19 18:43:00 N
1985/03/20 16:14:40 C
1985/03/21 11:59:00 N
1985/04/20 03:26:43 C
1985/04/20 05:22:00 New Moon
1985/05/19 21:42:00 New Moon
1985/05/21 02:43:51 C

1984/10/24 20:09:00 N
1984/11/22 11:11:33 C
1984/11/23 06:57:00 New Moon
1984/12/22 19:47:00 New Moon
1984/12/22 00:23:44 Center
1985/01/20 10:58:29 Center
1985/01/21 10:29:00 N
1985/02/19 01:08:19 C
1985/02/20 02:43:00 New Moon (Fake Leap Month)
1985/03/21 19:59:00 New Moon
1985/03/21 00:14:40 C
1985/04/20 13:22:00 N
1985/04/20 11:26:43 C
1985/05/20 05:42:00 N
1985/05/21 10:43:51 C

 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 Chinese Lunar 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
2033/10/23 10:28:44 C
2033/11/22 09:40:00 N
2033/11/22 08:17:18 Center
2033/12/21 21:47:08 Center

2033/12/22 02:47:00 N (Fake)
2034/01/20 18:02:00 New Moon

2034/01/20 08:28:25 Center
2034/02/18 22:31:19 Center

2034/02/19 07:11:00 N Fake)
2034/03/20 18:15:00 New Moon

2034/03/20 21:18:38 C
2034/04/19 03:27:00 N

2128/09/24 21:03:00 N
2128/10/23 11:04:51 C
2128/10/24 09:13:00 N
2128/11/22 20:26:00 N
2128/11/22 09:27:08 Center
2128/12/21 23:16:43 Center

2128/12/22 07:12:00 N (Fake)
2129/01/20 17:57:00 New Moon

2129/01/20 09:59:11 Center
2129/02/18 23:44:22 Center

2129/02/19 04:47:00 N (Fake)
2129/03/20 15:41:00 New Moon

2129/03/20 21:58:32 C
2129/04/19 02:48:00 N

2242/09/25 22:16:00 N
2242/10/24 01:54:53 C
2242/10/25 07:39:00 New Moon
2242/11/23 17:20:00 New Moon

2242/11/23 00:59:09 Center
2242/12/22 15:14:56 Center

2242/12/23 03:53:00 N (Fake)
2243/01/21 15:25:00 New Moon

2243/01/21 02:02:10 Center
2243/02/19 15:29:33 Center

2243/02/20 03:48:00 N (Fake)
2243/03/21 16:57:00 New Moon

2243/03/21 13:07:38 C
2243/04/20 07:00:00 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.

Different 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
2001/01/24 05:07:00 N
2002/02/11 23:42:00 N
2003/02/01 02:49:00 N
2004/01/21 13:06:00 N
2005/02/08 14:29:00 N
2006/01/29 06:15:00 N
2007/02/17 08:15:00 N
2008/02/06 19:45:00 N
2009/01/25 23:56:00 N
2010/02/13 18:52:00 N

2000/02/05 21:04:00 New Moon Time
2001/01/24 21:07:00 N
2002/02/12 15:42:00 N
2003/02/01 18:49:00 N
2004/01/22 05:06:00 N
2005/02/09 06:29:00 N
2006/01/29 22:15:00 N
2007/02/18 00:15:00 N
2008/02/07 11:45:00 N
2009/01/26 15:56:00 N
2010/02/14 10:52:00 N

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 solar segment times. The days of solar segment might fall on the different days among different time zones.

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
1680/11/21 08:52:54 Center
1680/12/20 21:05:31 Center
1680/12/21 01:45:00 N
1681/01/19 07:44:22 C
1681/01/19 19:51:00 N
1681/02/17 23:01:08 C Rain Water
1681/02/18 11:49:00 New Year Day
1681/03/20 00:00:49 C Vernal Equinox
1681/03/20 01:01:00 New Moon (Fake Leap Month)
1681/04/18 11:22:00 N

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
2052/12/21 04:18:32 Center
2053/01/19 15:00:35 Center
2053/01/19 23:13:00 N
2053/02/18 05:03:15 C Rain Water
2053/02/18 16:32:00 New Year Day
2053/03/20 03:48:44 C Vernal Equinox
2053/03/20 07:12:00 New Moon (Fake Leap Month)
2053/04/18 18:49:00 N

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
2071/12/21 19:05:49 Center
2072/01/20 05:47:04 Center
2072/01/20 06:37:00 N
2072/02/18 19:45:02 C Rain Water
2072/02/19 02:05:00 New Year Day
2072/03/19 18:22:59 C Vernal Equinox
2072/03/19 20:23:00 New Moon (Fake Leap Month)
2072/04/18 11:58:00 N

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
1719/01/20 12:33:00 New Year Day
1719/01/20 13:07:38 C
1719/02/19 04:17:35 C Rain Water
1719/02/19 06:44:00 N

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
1813/09/24 22:02:00 New Moon (Leap Month)
1813/10/24 13:40:00 9th New Moon
1813/10/24 03:05:23 Center
1813/11/22 23:28:33 Center
1813/11/23 07:44:00 10th New Moon
1813/12/22 12:07:40 Center - Winter Solstice
1813/12/23 03:14:00 11th New Moon
1814/01/20 22:45:21 Center - Severe Cold
1814/01/21 22:24:00 N 

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
2185/12/21 19:16:50 Center - Winter Solstice

2185/12/22 05:32:00 11th New Moon
2186/01/20 06:01:02 Center - Severe Cold
2186/01/21 01:17:00 N 

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
2001/06/21 11:58:00 Leap 05 2
2004/03/20 22:42:00 Leap 02 3
2006/08/23 19:10:00 Leap 07 4
2009/06/22 19:36:00 Leap 05 5
2012/05/20 23:48:00 Leap 04 6
2015/01/20 13:14:00 Leap 12 7

2017/07/23 09:46:00 Leap 06 1
2020/06/21 06:42:00 Leap 05 2
2023/03/21 17:24:00 Leap 02 3
2025/08/23 06:07:00 Leap 07 4
2028/06/22 18:28:00 Leap 05 5
2031/05/21 07:18:00 Leap 04 6
2034/02/18 23:11:00 Leap 01 7

 


2036/07/23 10:18:00 Leap 06 1
2039/06/21 17:22:00 Leap 05 2
2042/04/20 02:20:00 Leap 03 3
2044/08/23 01:07:00 Leap 07 4
2047/07/22 22:50:00 Leap 06 5
2050/05/20 20:52:00 Leap 04 6
2052/09/22 23:34:00 Leap 08 7

1998/06/24 11:51:00 Leap 05 1
2001/05/23 10:47:00 Leap 04 2
2004/03/21 06:42:00 Leap 02 3
2006/08/24 03:10:00 Leap 07 4
2009/06/23 03:36:00 Leap 05 5
2012/05/21 07:48:00 Leap 04 6
2014/10/24 05:57:00 Leap 09 7

2017/07/23 17:46:00 Leap 06 1
2020/05/23 01:39:00 Leap 04 2
2023/03/22 01:24:00 Leap 02 3
2025/07/25 03:12:00 Leap 06 4
2028/06/23 02:28:00 Leap 05 5
2031/04/22 00:58:00 Leap 03 6
2033/08/25 05:41:00 Leap 07 7

2033/12/21 21:47:08 C <- Double Center
2033/12/22 02:47:00 N 11 <- Fake
2034/02/18 22:31:19 C <- Double Center
2034/02/19 07:11:00 N 01 <- Fake
2036/07/23 18:18:00 Leap 06 1
2039/06/22 01:22:00 Leap 05 2
2042/03/22 01:24:00 Leap 02 3
2044/08/23 09:07:00 Leap 07 4
2047/06/23 18:37:00 Leap 05 5
2050/04/21 18:26:00 Leap 03 6
2052/09/23 07:34:00 Leap 08 7

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


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