Abstract
In ancient Japan as to avoiding solar eclipses like the plague, they had the notion of time that it makes no difference if an eclipse occurs in the daytime or at night. Even when an eclipse could not be actually observed because of sunset, they recognized it as a solar eclipse and refrained from duty at The Imperial Court. Many of the solar eclipses in the accounts were not actually observable from Japan. It was not due to calendar officials’miscalculation, but to their understanding of solar eclipses. They also predicted a solar eclipse which was not expected to be observable from the start, calling such a one 'night eclipse'.
Analyzing the accounts based on the above, the solar eclipse prediction and the skills of the calendar officials up to the 10th century can be summarized as follows. From the 8th century to the middle of the 9th century, there were almost no miscalculations in the solar eclipse prediction. That means the calendar officials at that time had enough skills to calculate quite accurately. However, after the enactment of the Xuanming calendar, the accuracy rate dropped significantly partly due to the omission in the calendar brought to Japan. The reason why at that time the prediction accuracy remained unimproved for some time would be that the calendar officials adopted a stance to firmly uphold the rules of the calendar from Tang.
