佛祖歷代通載 13.25

13.25

（十八　己巳）　初以上生日為千秋節○用大衍曆。

([Kaiyuan], Year 18, [cyclical year] Jisi) [729 CE]: For the first time, the Emperor's birthday was designated as the Thousand Autumns Festival. ○ The Dayan calendar was put into use.