Obon

Obon is kept on different dates in different parts of Japan, and the split has a precise cause: the adoption of the Gregorian calendar on 1 January 1873.

Before that, Obon fell on the fifteenth day of the seventh lunar month, late summer, after the heat had peaked, at full moon. The reform forced a choice, because the number and the season could no longer both be kept.

• Shichigatsu Bon, July Bon, kept the number. Regions that took this route observe July 13-15 in the new calendar. Tokyo, Yokohama and much of the Kanto and Tohoku do this.
• Hachigatsu Bon, August Bon, kept the season. Shifting a month forward to August 13-15 put the festival back roughly where the old seventh month had sat. Most of the country took this option, which is why the national travel peak and the corporate shutdown fall in mid-August.
• Kyu Bon, old Bon, kept the calendar. A minority of areas, parts of Okinawa, the Amami islands, and some rural districts, still calculate the fifteenth day of the seventh lunar month, so their Obon moves every year and can fall anywhere from late August into September.

The consequence is that Japan has no single national Obon date, only a dominant one, and that the answer to when Obon is depends on which prefecture is asking.

The story underneath

The framing narrative is the Ullambana Sutra: Maudgalyayana, greatest of the Buddha's disciples in psychic power, looks for his dead mother and finds her among the hungry ghosts, unable to eat. He is told he cannot free her alone and must make offerings to the whole assembly of monks at the close of the rains retreat. The sutra is generally judged by scholars to be a Chinese composition rather than a translation from an Indian original, shaped by Chinese concern with filial duty. Beneath the Buddhist frame there is older Japanese practice around the returning dead, and the festival is best read as the two settled onto one another.

Bon Odori, communal dancing performed during Obon to welcome and entertain the spirits of the returning dead, takes strikingly different regional forms across Japan, and the best known, Tokushima's Awa Odori, transforms the entire city for four nights in mid-August into a continuous street performance, with organised dance troupes called ren, some hereditary and centuries old, parading through closed-off streets to a driving rhythm of shamisen, drums and flute while hundreds of thousands of visitors watch or join in, making it one of the largest dance festivals anywhere in the world and, for many Japanese people today, the most visible and recognisable image of Obon itself.

Smaller-scale Bon Odori, typically a simple circular dance performed around a central raised platform, the yagura, to recorded or live folk music, remains a standard community event at shrines, temples and neighbourhood associations across the whole of Japan and within Japanese diaspora communities overseas, including in Hawaii and the continental United States, where Buddhist temples serving Japanese-American communities have kept Obon dance festivals running continuously for many decades as one of the clearest surviving threads of Japanese religious and cultural practice in the diaspora.