Chinese Leap Lunar Months

First, we need to know the difference between the Chinese Astronomical Calendar and the Civil Calendar. The Chinese Civil Calendar is posted by the Chinese government. The Chinese Astronomical Calendar is used by astronomers who work for government. The Astronomical Calendar is much more accurate than the Civil Calendar. The major difference is the assignment of leap months. We know a leap month is assigned if a lunar month (new moon to new moon) has no Solar Center Point. But, what do we do when the new moon day and the Solar Center Point fall on the same day?

If the new moon day and the Solar Center Point are on the same day, the lunar month contains that Solar Center Point in the Civil Calendar system. In the Astronomical Calendar, we have to compare the new moon time and the Solar Center Point time (hour, minute and second). The lunar month contains that Solar Center Point only if the Solar Center Point time comes after new moon time.

Because they are different, the listing of leap month assignments is different. From the following comparison charts of Beijing Time, PST and EST from 1979-2001. We find

China Beijing Time or Taiwan Standard Time  - Longitude East 120th degree
China Civil Calendar China Astronomical Calendar
Year New moon Leap  month Year New moon Leap month
1979 07-24 09:41 06 1979 07-24 09:41 06
1982 05-23 12:40 04 1982 05-23 12:40 04
1984 11-23 06:57 10     N/A
1985 02-20 02:43 01 (Removed) 1985 04-20 13:22 03
1987 07-26 04:37 06 1987 08-24 19:59 07
1990 06-23 02:55 05 1990 06-23 02:55 05
1993 04-22 07:49 03 1993 05-21 22:06 04
1995 09-25 00:55 08 1995 10-24 12:36 09
1998 06-24 11:50 05 1998 07-23 21:44 06
2001 05-21 10:46 04 2001 06-21 19:58 05

 

Pacific Standard Time (PST) - USA Longitude West 120th degree
Civil Calendar Astronomical Calendar
Year New moon Leap  month Year New moon Leap month
1979 06-24 03:58 05 1979 07-23 17:41 06
1982 05-22 20:40 04 1982 05-22 20:40 04
    N/A     N/A
1985 03-21 03:59 02 1985 04-19 21:22 03
1987 08-24 03:59 07 1987 08-24 03:59 07
1990 06-22 10:55 05 1990 06-22 10:55 05
1993 05-21 06:06 04 1993 05-21 06:06 04
1995 09-24 08:55 08 1995 10-23 20:36 09
1998 07-23 05:44 06 1998 07-23 05:44 06
2001 06-21 03:58 05 2001 06-21 03:58 05

 

Eastern Standard Time (EST) - USA Longitude West 75th degree
Civil Calendar Astronomical Calendar
Year New moon Leap  month Year New moon Leap month
1979 06-24 06:58 05 1979 07-23 20:41 06
1982 05-22 23:40 04 1982 05-22 23:40 04
    N/A     N/A
1985 04-20 00:22 03 1985 04-20 00:22 03
1987 08-24 06:59 07 1987 08-24 06:59 07
1990 06-22 13:55 05 1990 06-22 13:55 05
1993 05-21 09:06 04 1993 05-21 09:06 04
1995 09-24 11:55 08 1995 10-23 23:36 09
1998 07-23 08:44 06 1998 07-23 08:44 06 06
2001 05-22 21:46 04 2001 06-21 06:58 05

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