The Korean characteristics in the history of Korean astronomy during the King Sejong (r. 1419-1450) period can be properly understood only when examined with a focus on knowledge and activities, not on the theoretical but on the practical dimension. Indeed, in this period, Joseon Korea hardly developed an independent and unique astronomical theory, differing from that of China. Nor did the kingdom ever seek to develop and implement an independent calendrical system. In addition, Korea during this era did not produce its own astronomical instruments, differing from those of China. Nor were astronomical observational activities using astronomical instruments carried out for the purpose of developing new theories and securing new data. On the contrary, the intention of astronomical observations made in Joseon was to confirm the validity of the time standard established by the dynasty. The history of Korean astronomy during this period was one that consisted of research and activities for establishing and implementing the nation’s time standard. Consequently, the Korean characteristics of the atronomy in this era was most pronounced in the implementation of a time standard. This is why the nation’s uniqueness and independence reached their height in the diverse clocks created during the Joseon Dynasty.