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My understanding is that you don’t need the direct sunlight, just the rays from the Sun, which is abundant, even on cloudy days?

My understanding is quite the opposite. You need UVB light which is blocked by clouds and by glass.

See post #19. The reason you can't make vitamin D in the winter, at higher latitudes, is that the Sun is low to the horizon. At that attitude the atmosphere blocks UVB. Think about it and that would apply to the early and late hours even in the summertime.

The info in post #19 made me think about how much beneficial sunlight I actually get and I decided that I don't get much. So I supplement.