Where the boundaries come from
Golden hour is the stretch when the sun is low enough that its light travels a long way through the atmosphere, which scatters away the blue and leaves the warm end of the spectrum. We take it as the sun between 4° below the horizon and 6° above, which is the convention most photographers use. Blue hour follows it: the sun between 6° and 4° below, when the sky is lit but the sun itself is gone.
These are conventions, not physics. Nothing changes at exactly 6°. Another site may use slightly different limits and be equally correct, which is why our city pages say what we used.
It is not an hour
How long golden hour lasts depends entirely on how steeply the sun crosses the horizon. At the equator it goes almost straight down and the whole thing is over in about 20 minutes. In London in June the sun slides along at a shallow angle and golden hour runs for well over an hour. In Reykjavík in June it can last most of the night.
That is why every city page gives you the morning and evening windows as real times for that place and that date, rather than telling you to turn up an hour before sunset.
Blue hour is the one people miss
Most people pack up at sunset. Blue hour starts afterwards and lasts a similar span: the sky holds a deep even blue while artificial lights come on at roughly the same brightness, which is the only time of day a city reads as lit without being a mess of hot spots and black.
Finding yours
Every city page shows today’s golden hour for morning and evening, and blue hour for the evening, with the exact minutes. The sky bands behind the sun’s path on the same page are coloured on the same scale, so the band under any point on the curve is the colour of the sky at that moment.
