He was the first to see the curvature of the earth and the sky dark at mid-day.

It must be close to dawn, though the rain kept the sky dark.

It was ten o'clock in the morning, the sky dark, heavy rain imminent.

I glanced back at the stump of stone behind us, and saw the eastern sky dark with fast-approaching night.

It was 2 a.m., the sky dark without a moon.

The shadows were lengthening and the sky growing dark.

The weather showed its most unfriendly side: sky dark, water as grey as lead.

I asked, chewing, the sky dark through the windows as the day now came to an end.

With the sun finally gone and the clear sky dark, they manned their aircraft and lifted off for a night's testing.

I'm so tired, I couldn't turn the sky dark at nightfall.