There isn’t one universal “best” time for black-and-white landscapes—it depends on the mood and contrast you want.

For many landscapes, dawn and dusk are strong choices because the light is lower, more directional, and often gives better tonal contrast than harsh midday sun. These times can make scenes look more interesting and dimensional.

If you want darker skies and strong cloud contrast, daytime can work well too, especially when converting from color to black and white in post. Different color-channel mixes during conversion can dramatically change how the sky and clouds render.

For city skylines, early evening can be ideal when there’s still some brightness in the sky but artificial lights are turning on. More experimental looks are also possible at night or even by moonlight with long exposures.

So the key is not black-and-white specifically, but matching the light to your intended result. Shoot in color if you want maximum editing flexibility, and experiment with different times of day and weather conditions.