A record of "double dawn" at State Zheng in the first year of the reign of
King Yi in Western Zhou Dynasty in the chronicle "Bamboo Annals" (Zhushu Ji
nian) is discussed. We think that it may be a record of an annular solar ec
lipse happening in 899 BC. The record and the Delta T, which describes the
secular Variation of the earth's rotation, are analyzed and discussed.