三時年限

The three periods of Buddhism-- 1,000 years of 正法 pure or orthodox doctrine, 1,000 years of 像法 resemblance to purity, and 10,000 years of 末法 decay. Other definitions are 正 and 像 500 years each, or 正 1,000 and 像 500, or 正 500 and 像 1,000.