expression
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.
夜更けてから、ようやく仕事が終わった。
Late at night, I finally finished my work.
夜更けて、街は静まり返っていた。
Deep in the night, the town was completely silent.
夜遅く is a more common and neutral way to say 'late at night', while 夜更けて has a slightly more literary or descriptive feel, emphasizing the deepening of the night.
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'.