late at night; deep in the night
Describes a time when the night has grown late and quiet. Often used in literary or descriptive contexts.
Late at night, I finally finished my work.
Deep in the night, the town was completely silent.
Kana-mixed spelling; the kanji 更 is sometimes written as kana.
From 夜 (night) + 更けて (the -te form of 更ける, 'to grow late'). The phrase literally means 'the night having grown late'.