Qijuzhu 起居注 "imperial diaries" are protocols of emperor's daily activities. For this purpose, there were scribes (shi 史) that noted down the sayings and doings of a ruler. During the Han period 漢 (206 BCE-220 CE) this task was taken over by female officials (nüguan).
The Northern Wei 北魏 (386-534) created the office of the assistant diarist (qiju lingshi 起居令史), the Tang 唐 (618-907) court employed an imperial diarist (qijulang 起居郎) who was assisted by a certain staff.
Fragments from the earliest imperial diaries are surviving from the time of Emperor Wu 漢武帝 (r. 141-87 BCE) of the Han period, the Jinzhong qijuzhu 禁中起居注, and the Mingdi qijujuzhu 明帝起居注 from the early Later Han period 後漢 (25-220 CE). Imperial diaries are important sources for the policital history of China.
The book Da-Tang chuangye qijuzhu 大唐創業起居注 is not an imperial diary in the proper sense, but a chronicle.