noun
five-period night division
Archaic system dividing the night (roughly 7pm–5am) into five equal two-hour periods. Used in historical contexts.
江戸時代には、夜を五夜に分けて時刻を知らせた。
In the Edo period, the night was divided into five periods to tell the time.
noun
fifth night period (approx. 3am–5am)
Specifically the last of the five periods, corresponding to the pre-dawn hours. Also archaic.
五夜は夜明け前の最も暗い時間帯とされた。
The fifth night period was considered the darkest time before dawn.