The Longest Day in Chang'an

The year is 744, the Tianbao era under Emperor Xuanzong, and the night is the Lantern Festival, the fifteenth of the first lunar month, when Chang'an lifts its curfew and the whole city goes out. Word reaches the Jing'an Si (靖安司, "the Pacification Office", the city's security bureau) that a plot is moving against the capital. Li Bi (李必), a young official of the office, is racing the clock. He turns to Zhang Xiaojing, a prisoner under sentence of death, and offers him a day's reprieve to stop it.

The structure is the point. Chinese time was counted in shichen (时辰, "double-hours"), twelve to the day, each two hours long, and the series is built on twelve of them. Each episode covers about thirty minutes. Director Cao Dun (曹盾) said the team set out not to make an American-style 24.

The drama is adapted from the novel by Ma Boyong (马伯庸). Cao Dun came to directing from cinematography, and has said the real protagonist is Chang'an itself. The art department built the exterior city at the Xiangshan film studio, with streets at true width: the main avenue, Zhu Que Street, ran roughly 120 metres wide. Production designer Jin Yang (金杨) said the aim was to recreate one day of the Tang as faithfully as possible, working from archaeological finds and documents. According to Cao Dun, no costume was rented.

The praise is mostly about what the camera sees; the criticism is about how the story moves. PingWest (品玩) said the rhythm slowed noticeably after episode 20. Douban (豆瓣), China's main user-review site, held the show at 8.5 when the finale aired in August 2019. The 24 comparison fits the structure and misses what is distinctive: 24 is about an agency, and this is about a city.