The Major Events in the Chinese Calendar Reform History
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The First Day of the Year
Shiah
Dynasty (2205 B.C.) used the 
Tiger month as
the first month of the year
Chou Dynasty (1122 B.C.) used the 
Rat (Winter Solstice) month as the first month of the year
Yin Dynasty (1401 B.C.) used the 
Cow month
as the first month of the year
Chin Dynasty (221 B.C.) used the
Rat month as the first month of the year
Han (104 B.C.) used the Tiger month as
the first month of the year
Cow month
as the first month of the year for a short period
The Beginning Time of a Lunar and Solar Months
In order to find out the good solution for the Lunar Leap
month, ancient Chinese astronomers had been looking for the common cycle of
Sun and Moon. They studied the length of lunar and solar months, the length of
a day and year, the number of lunar months in a year and so on, then made many changes in the calendar system. For example, in
Yin Dynasty (1401 B.C.), Chinese
calendar determined a Leap Month by a lunar month without a Sector
Point instead of a Center Point. The major changes in the Chinese calendar reform history
were the definition of
the beginning time of a lunar month and a solar month.
Before 619 A.D., Chinese used 
Mean Moon times and
Mean Sun times to determine the Leap Months over one thousand
year long.
After 619, during 
Tang Dynasty, Chinese used 
True Moon times and
Mean Sun times to assign the Leap Months for about another one thousand
year. That means the new moon time is much easier to observe than the sun longitude position in the sky.
After 1645, 
Ching Dynasty, Chinese used
True Moon times and
True Sun times to find the Leap Month
locations. That's because Ching Dynasty imported modern astronomical instruments and had the ability to observe precise the Sun and Moon positions in the
sky during years.
The Mean Moon time is the length of a lunar month is the average length of lunar months a year.
The True Moon time is the length of a lunar month is the length between two new moons.
The Mean Sun time is the length of a solar month is the average length of solar months in a year.
The True Moon time is the length of a lunar month is the length between two solar Sector Points.
After Ching Dynasty, China government began to use
the Gregorian Calendar instead of lunar month for daily activities.
The First Day of Chinese Calendar Cycle
Many ancient Chinese astronomers in different dynasties kept trying to calculate back and searching for the beginning of the Chinese Calendar cycle. The theoretic day of the starting point of Chinese Calendar is that the day must be
Wood Rat Day, the first day of 60
Stem-Branch cycleThey all failed to get the satisfied answer.
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