They turn the light on at dark.

他们天黑时开灯。

youdao

Production of the sleep hormone melatonin begins at dark.

睡眠荷尔蒙褪黑素在夜间开始分泌。

youdao

The night was dark and quiet; my blood ran cold when I heard a strange noise outside at dark night.

夜晚黑暗而宁静；漆黑夜色中听到外面有奇怪的声响，我感到毛骨悚然。

youdao

She is easily frightened. For example, she is too chicken-livered to walk down a dark street alone at night.

VOA: special.2010.06.13

First,they don't meet in the daytime; they meet either early before light,at dawn, or after dark,at night.

首先，他们不在白天聚会;,要么在天亮前的黎明，要么在天黑后的夜晚。

耶鲁公开课 - 新约课程节选

Next time we'll take a look at the Dark Ages and the world of Homer.

下一节课我们会学习,黑暗时代和荷马所在的世界

耶鲁公开课 - 古希腊历史简介课程节选

So at dark John Henry came to the back door with a little weekend bag.

NPR: Excerpt: 'The Member of the Wedding'

It hints at dark consequences.

ECONOMIST: Fiscal Armageddon, coming to a cinema near you

And at least once a week she will kneel on the mattress before you and, with one hand pulling at her dark nipples, will play with herself, not letting you touch at all, fingers whisking the soft of her and her face looking desperately, furiously happy.

NEWYORKER: Alma