Annual Sunlight Planner

Worked example

At a mid-latitude location such as New York City, the June solstice has noticeably more daylight than the December solstice, since the sun's angle above the horizon is much higher during the local summer than during the local winter. An equinox date falls close to twelve hours of daylight almost anywhere on Earth, sitting roughly halfway between the two solstice extremes at a mid-latitude location. Nearer the equator this seasonal swing shrinks toward almost nothing, while much closer to the poles it grows toward the full extremes of a true polar day with no sunset at all or a polar night with no sunrise at all.

Common mistakes

• Comparing dates at very different latitudes and expecting a single consistent seasonal pattern. The size of the swing between solstices depends heavily on latitude.
• Forgetting that a polar day or polar night date has no ordinary sunrise or sunset at all, which this reports directly instead of an invalid time.

Limitations

This uses the same NOAA General Solar Position model as WhenMath's other daylight engines, verified against equinox and polar-day and polar-night reference cases, and it does not account for local terrain or weather that could obscure an actual sunrise or sunset.