The founding time of the Khitan Empire in the literature system of the Liao is the year 907, which contradicts historical facts. However, the historical narrative on this political time seem holistic and systematic, so it was not a result of the historians’ negligence but of a deliberated choice. In fact, there have been two very different writings in the official history of the Khitan dynasty: the account of “Junji Taiyi appeared several times” in the Taizu Ji of the Liaoshi was an auspicious rumor created by the Han Chinese counsellors around Abaoji on the eve of the first year of Shence era (916), which reflects the original historical event; the other records we usually use have been completely rewritten by the later historians, real and original date of the empire’s foundation was thoroughly smeared and covered. The relevant rewriting work may be completed in the 13th year of the Emperor Xingzong’s Chongxi era (1044), and Abaoji’s intronisation date was advanced to the year of Tang Dynasty’s demise. Because this event is essential to the dynastic and pre-dynastic history of the Khitan, its rewriting reflects the requirement of a stronger legitimacy of the political power during the late Liao Dynasty. Through this typical case, we may try to rethink the importance of political timing in ancient historical writing from a more dynamic and generating perspective.