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| Date |
Event |
| 2637BC |
Earliest recorded use of some form of
calendar system was during Emporer Shih Hwang Ti's reign. During his 61st
year reign he introduced the 1st cycle of the Zodiac (which we now
referred to as the Sexagenary Cycle).
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| 2000BC |
The Chinese divided the Equator into 24 segments, each 15° in
longitude. The period taken by the Sun to traverse each segment is called
a chi (approx. 15.23 days). Each chi is given a name,
eg. Li chun is the time when the Sun's true longitude is
between 315° and 330° meridian.
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| 1500BC |
Chinese astronomical knowledge was inscribed onto Oracle
bones. Records include sightings of novas, supernova and bright comets.
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| 1300 BC |
The Chinese figured out the solar year was approximately 365.25
days and the synodic month to be about 29.53 days.
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| 700BC->300BC |
Earliest known almanac - Xia Xiao Zheng, primarily a
farmers calendar. Later versions contained more astronomical data,
allowing the determination of the number of days in a month and number of
months in a year.
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| 370BC->270BC |
Earliest attempts to catalog various stars.
The catalogue contained 1,464 stars. The position of the star was
described by 3 parameters. The celestial sphere was divided into 28
unequal segments or xiu (lines joining Nth-Sth pole). Each xiu
was named after a constellation that it contained (eg: Fang, Xin, Wei,
etc). Angular measurements (du) was also used - there are 365¼ du's
to a complete circle. A star's was specified as 101 du from the pole, 42
du from the beginning of Xin and how far from the edge of the xiu.
This is analogous to current days use of longitude / latitude,
azimuth / altitude or right ascension / declination to pinpoint a star.
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| 350BC |
Shih Shen knew the Moon moved irregularly. By contrast, the Sun's irregularity was only discovered in 570AD. The
Moon's irregular
motions were only incorporated into the almanacs later in 200AD.
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| 200BC |
Astronomical knowledge improved significantly and the data
was quite precise.
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| 90BC |
Earliest known detailed description in China of the motion
of the planets.
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| 29BC |
Chinese astronomers observed Sun spots by looking through slices of Jade.
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| 20BC |
Chinese knew how eclipses were caused, though there were some disagreement.
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| 8BC |
Predict eclipses using the 135-month period.
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| 7BC |
Best known almanac - The Sun Tong contained relatively accurate
data for the Sun, Moon and the planets.
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| 104BC->1912AD |
Many minor calendar reforms.
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| 9AD |
Elaborate tables of planetary motions compiled.
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| 100AD |
Si Feng - earliest almanac of planetary motions
published.
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| 200AD |
Moon's irregular motion incorporated into almanacs.
Almanacs
of this period included procedures for calculating the name of the current
Metonic cycle (76-year cycle), occurrence of the 13th month (intercalary
or leap month) and the number of days in a month (29 or 30). Ability to
calculate the date of new moon (conjunction).
Earliest recorded usage of the 19-year Chang (章) cycle (or Metonic
cycle as is know today). Chinese used a variant or 4 Bu (=76
years). The Chang cycle is 0.4 days longer than 19 tropical years
(=1.2 days in 76 years), whereas the Bu cycle is only 0.6 days
longer that the 76 tropical years and thus more accurate.
It is believed that some of these knowledge may have originated from
Babylonia.
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| 206AD |
Able to predict eclipses by analyzing the motions of the
moon.
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| 309AD |
Able to predict how much the moon would be in shadow.
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| 462AD |
Da ming almanac devised by Zu Chongzhi gave the
length of a year to be 365 + 9.589/39.491 = 365.242815 days. In the West
at that time, the most accurate was Ptolemy's 365.2467 days.
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| 570AD |
Irregularity of the Sun's motion discovered.
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| 600AD |
Pairs of 15° segments were combined to form signs of the
zodiac which was borrowed from Babylonia through India. The signs were
named after animals.
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| 604AD |
Liu Chuo developed an arithmetic technique (similar to the
Babylonian system in principle) to deal with the irregularities of the Sun's motion.
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| 724AD |
Discovered that the change in shadow length (pole elevation)
is proportional to the north-south distance.
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| 1912AD |
Gregorian calendar adopted by China, calendar comprised
months with 29/30 days. There were a further 42 reforms made to the
Chinese calendar. |
