TSU CH'UNG CHI c.430  c.501 Chinese Mathematician 

Tsu Ch'ung Chi, mathematician and astronomer, who calculated the value of pi to 8 decimal places, and determined the precise time of the solstice. No mathematician since his time, computed a value of pi this precise until another 1000 years.
Tsu Ch'ung Chi calculated one year as 365.24281481 days, which is very close to 365.24219878 days as we know today. He also calculated the number of overlaps between sun and moon as 27.21223, which is very close to 27.21222 as we know today; using this number he successfully predicted an eclipse four times during 23 years. 
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