Bon, or more politely O-Bon, is the Japanese term for a regionally different midsummer festival celebrated not only throughout Japan but also in other Buddhist Asian countries. In Japan, it has changed over time and is essentially a mélange of ancestor worship, rural Thanksgiving customs, ghost beliefs, folk religion, superstitions and the Buddhist celebration of the temporary release of the spirits from hell. During the Edo period, O-Bon gained popularity, as it gave those employed in urban areas a rare chance to reunite with their families in the countryside, meet friends, revel, and pray for ancestral spirits and deceased loved ones. Celebrations differ from region to region, but they all include eating, drinking, and lots of merrymaking to entertain the living as well as the visiting spirits. Since the 7th century, O-Bon has been held on the full moon of the seventh lunar month, usually around the 15th day. The old calendar is still the basis for the calculations behind the traditional Chinese festival calendar used in both mainland China and Taiwan. However, since Japan adopted the solar Gregorian calendar in 1873, Japan became divided into different areas: some celebrating O-Bon in July (Shichigatsu-Bon, 七月盆), some regions sticking to the old lunar calendar with movable holidays, and some areas holding a Hachigatsu-Bon (八月盆) from August 13th to 15th. During the Edo period, Nagasaki's Japanese O-Bon and Chinese O-Bon fell on the same dates. Due to the calendar reform, they came to be held on separate days. As a result, Nagasaki now celebrates two festivals: 1. a movable lunar O-Bon in July, locally called Karadera-Bon (唐寺盆) or Achasan no Bon (アチャさんの盆or 阿爹さんの盆) with strong connections to the city's Chinese temples and traditions, where it is called Yúlánpén (盂蘭盆) and 2. a Hachigatsu-Bon, celebrated by Japanese citizens, which reflects Nagasaki's' unique culture, history and customs. In this paper, I would like to shed some light on the origins, religious aspects, traditions, practices, and social function of Nagasaki's' two O-Bon celebrations. [ABSTRACT FROM AUTHOR]