It will be cooler when the sun has set.

太阳落山之后会凉快一点。

youdao

After the sun has set, the night is dark.

太阳西下，夜晚一片黑暗。

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It works on cloudy days and when the sun has set.

这种石头在阴天和太阳落山时仍然有用。

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Now the sun has set, Bur Dubai Souq (between Al-Fahidi Street and Dubai Creek) is buzzing.

BBC: A perfect day in Dubai

They say it works on cloudy days, and when the Sun has set.

BBC: 'Viking sunstone' found in shipwreck

But for a solar eternal plane to be exactly that it needs an efficient energy harvesting, conversion and storage system that will work when the Sun has set.

BBC: NEWS | Science/Nature | 'Eternal planes' to watch over us