Sunrise Sunset Calculator

In short Sunrise and sunset are worked out from three things: your latitude, the sun declination on that date, and the altitude the sun has to reach. That last one is not zero, and it is where most confusion starts. Sunrise is defined on the sun UPPER LIMB rather than its centre, which gains you the sun own radius of about 0.267 degrees, and atmospheric refraction near the horizon lifts the whole image by roughly 0.567 degrees. Together that is the standard −0.833 degrees, and both effects make the day longer — neither cancels the other. It is why the sun you see touching the horizon has geometrically already set. Solar noon is almost never 12:00 either. Two separate things move it: the equation of time, which runs from about −14.2 to +16.5 minutes across the year because the earth orbit is an ellipse and its axis is tilted, and your longitude relative to the centre of your time zone, which shifts it by four minutes per degree. Clock noon and sun noon coincide on roughly four days a year and can be more than half an hour apart otherwise. Above the Arctic circle and below the Antarctic there are dates with no sunrise or no sunset at all, and the honest answer there is to say so rather than to invent a time — polar day begins where the latitude exceeds 90 degrees minus the sun declination, and refraction pushes the real boundary about 50 arcminutes further out than the geometry alone suggests.