We arranged ancient Korean calendar during Koryo dynasty (A.D. 918-1392) according to Julian calendar. We used two representative history books, Koryo-sa (高麗史) and Koryo-sa Jeolyo (高麗史節要), which contain thea stronomical and the historical records chronologically. We found all 19,727 ganji dates(日辰) and 102 misrecoreded ganji dates in two books. Most of the data are arranged based on those two books, and doubtful data are identified using the eclipse, historical events and lunar phase calculations etc. Although Korea, China, and Japan were using basically the same calendar since ancient times, their calendars show some significant disagreement. We found that arranged chronological tables during Koryo dynasty were, in some cases, different from those of China and Japan.

• 양홍진(한국천문연구원/경북대학교 천문대기과학과) | YANG HONG JIN (Korea Astronomy Observatory, Department of Astronomy and Atmospheric Science, Kyungpook National University)
• 안영숙(한국천문연구원) | AHN YOUNG SOOK (Korea Astronomy Observatory)
• 한보식(한국천문연구원) | HAN BO SIK (Korea Astronomy Observatory)
• 심경진(한국천문연구원) | SIM KYUNG JIN (Korea Astronomy Observatory)
• 송두종(한국천문연구원) | SONG DOO JONG (Korea Astronomy Observatory)