As smackay mentions, there are different 'definitions' of twilight [1], I went with the 'civil' one, which is the most widespread. The page could be modified t

As smackay mentions, there are different 'definitions' of twilight [1], I went with the 'civil' one, which is the most widespread. The page could be modified to present a gradient, since it only requires calculating the sun's altitude and solar time, which is not that complicated. [1] https://en.wikipedia.org/wiki/Twilight https://en.wikipedia.org/wiki/Twilight