A way of measuring the year was invented during the age of the Three Emperors, 30-50,000 years ago, according to Szu-ma Ch'ien's first-century B.C. Records of the Grand Historian.
根據史記三皇本紀記載，先民早在三、五萬年前的「天皇氏」時期，就有紀年之法了。