Korea Astronomy and Space Science Institute (KASI) has constructed online database of the Korean Astronomical Almanac as a part of the 'Knowledge and Information Business Project 2009' supported by the Ministry of Knowledge Economy. Throughout this project, KASI provides both digitized images and extracted text from the almanac covering approximately 240 years. The primary purpose of this paper is to serve as a reference for users of the almanac database. Hence, we introduce the calendar history and kinds of the astronomical almanac used in Korea, and explain the contents of the almanacs according to its appearance time. We also briefly mention the steps employed in constructing the database system and Web site. Since ancient times, astronomical almanacs have been an essential part of daily life. We, therefore, believe that the astronomical almanac database constructed by KASI will prove its usefulness in various fields, and particularly in the study of historical astronomy.

We have constructed a database of Korean historical astronomical records. The database contains observational data recorded from BC 2183 to AD 1910. We have also built a webpage for searching through the database based on the following criteria: (1) dynasties (2) astronomical phenomena (3) reigning kings (4) references (5) keywords. Users may select two or more dynasties to search through the database for a certain phenomena, and compare data with those of other dynasties. The queried data can be primarily sorted by one critetion, and secondarily sorted by another, each in ascending or descending order. The search results give dates both in Solar and Lunisolar calendars, years and dates in Sexagenary cycle, dynasties, reigning kings, astronomical phenomena, and references. The database and webpage were constructed under the research project of the Korean Astronomical Data Center (KADC, http://kadc.kao.re.kr) in Korea Astronomy Observatory (KAO).