The number to know is 365. At dusk on June 5, in the cedar-dark grounds of Atsuta Jingu — the 1,900-year-old Nagoya shrine that guards the sacred sword of the imperial regalia — five towering hemispheres of woven straw are hoisted and lit, each dressed with exactly 365 paper lanterns: one for every day of the year, a prayer for health hung day by day into a single burning constellation. These kento makiwara are the emblem of the Atsuta Matsuri, the shrine's grandest festival, when an imperial envoy attends the morning rites and the whole city, by long agreement, declares summer begun. Nagoyans traditionally wear their first yukata of the year tonight.

The day runs in movements: solemn ceremony at ten, then martial arts, tea, and flower offerings through the afternoon in the forested precincts, then the lantern towers at dusk — and at 7:40, fireworks. About a thousand shells rise from the neighboring park, which means you watch them not across water, as at most Japanese fireworks festivals, but over the canopy of an ancient sacred forest, lanterns glowing below, treetops silhouetted against the bursts. It is an entirely different geometry of hanabi.

Some 200 food stalls line the approaches from the evening before, and Jingu-mae Station is three minutes from the gates — office workers arrive straight from work, jackets over shoulders. Free, unticketed, and fixed to its date whatever the weather portends: June 5 is when summer starts in Nagoya, and has been for a very long time.