Chiljeongsan-Naepyeon (七政算內篇; hereafter, Naepyeon) is a type of astronomical calendar that was used by the Joseon dynasty of Korea. The book of Naepyeon, compiled by Yi, Sunji (李純之) and Kim, Dam (金淡) in 1442, lists the times of sunrise and sunset at Hanyang (漢陽; the capital of the dynasty, which is present-day Seoul). The listed times have very high accuracies, approximately less than or equal to 1 min, compared with the accuracy of the calendar itself. Naepyeon is known to be fundamentally the same as Sushili (授時曆), which was made by Guo Su-Jing (郭守敬) in the Yuan dynasty or Datongli (大統曆) in the Ming dynasty of China. Sushili is currently evaluated as one of the best calendars throughout the history of the Chinese calendar. In this work, we study the times of sunrise and sunset in Naepyeon. First, we investigate the measurement procedures used to obtain the sunrise and sunset times in Sushili, referring to Yuanshi (元史; the history of the Yuan dynasty) and Mingshi (明史; history of the Ming dynasty). Then, we reproduce the times of sunrise and sunset at Beijing given in the literature. We found that various mathematical methods - Hushigeyuan (弧矢割圓; an approximation method for calculating an arc) and Zhaochafa (招差法, an interpolation method using a cubic equation), which includes the Pythagorean theorem - were used in Sushili to measure those times, together with observational data - the latitude and obliquity of the ecliptic, which were derived from the shadow lengths of the Guibiao (圭表; gnomon) on the summer and winter solstices. Finally, we calculate the times of sunrise and sunset according to the latitude based on the measurement procedures in Sushili and estimate the latitude used in Naepyeon by comparing the results of our calculations with the times presented in the book of Naepyeon.