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 animation uses a "hot metal" colour scale that begins at dark red and progresses through orange and yellow to white at the highest levels of activity.

影片里用色线标出了活动等级：由深红开始，逐步过渡桔红，再到黄色，进而显成白色这一最高等级。

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

The first candidate to sit down at the dark-stained conference table was a Chinese-American, from Washington state, named Andrew Hsu.

NEWYORKER: No Death, No Taxes