This paper examines the calendars published in the Joseon period, focusing mainly on the changes in their outward form. The significant changes in the outward forms of Joseon calendars were made twice during about five hundred years of the dynasty. The first change was made after the Japanese invasion in 1592, and the second after the Manchurian invasion in 1637. While examining the causes of the changes, I investigate the material aspects and the basic conditions of the autonomous calendar-publishing by Joseon government. With this examination, I argue that the changes in the outward forms of Joseon calendars were not caused by the developments of calendar calculation method, but caused by the changes in the tributary system that regulated the relation between ``China as a Empire`` and ``Joseon as a Feudal State``. I also argue that if the local science of calendar calculation system had existed in Joseon, the most essential condition that enabled it was the practical demand for calendars that could be met by investing vast resources. In addition, in the process of satisfying such demand, the distance between Seoul and Beijing was too far just to wait for the arrival of Chinese calendars. Joseon government had no choice but to study the calendar calculation method independently for autonomous calendar publication.