Time line: Abacus calculation in China

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ABACUS CALCULATION IN CHINA

1095-90 BC: Earliest date of possible origin of abacus calculation in China. Supported by the 1976 archaeological discovery of 90 ceramic beads in Qi county, Shaanxi province. But some believe the beads are instead ammunition for such toys as slingshots.

AD 1st-2nd centuries: Methods for computing square roots, cube roots and other complex operations using counting rods were recorded in Jiuzhang Suanshu, or Nine Chapters on the Mathematical Art - one of China's earliest mathematical texts.

AD 561-577: The Chinese expression zhusuan, or abacus calculation, first appeared as one of the 14 calculation methods in Shu Shu Ji Yi, or Notes on Traditions of Arithmetic Methods. Other methods included counting rods, mental arithmetic and the like. It's believed the abacus had by then taken a form like today's.

1102-1110: A suanpan, or abacus, first appeared in a painting. This is direct evidence of its spread as a calculation tool. In the painting Riverside Scene at Qingming Festival, created by Zhang Zeduan (1085-1145), the suanpan can be seen on an herbal medicine shop's desk.

1403-1425: Standardized measurements of all the parts of an abacus, indicating the sizes of the rods and frames, were recorded in The Carpenter Classic of Lu Ban. The book was compiled during Ming Dynasty (1368-1644) emperor Yongle's reign.

1929: An abacus bead was unearthed in Julu county, Hebei province. The 2.11-centimeter-wide wooden bead resembles the beads used today. It is the oldest abacus bead found and dates to 1108, during the Song Dynasty (960-1279).

1979: The Chinese Zhusuan Association's founding conference was held in Qinhuangdao, Hebei province, gathering more than 200 representatives from home and abroad.

1987: The first monograph of the abacus' history was published. Written by Hua Yingchun, Chinese Abacus History provides a holistic account of the device's origin and development.

2013: Chinese zhusuan, or the knowledge and practices of abacus arithmetic calculations, was inscribed on the Intangible Cultural Heritage list at the eighth annual UNESCO World Heritage Congress on Dec 4 in Baku, Azerbaijan.