Twilight & Golden Hour Planner

Times are local clock times for the UTC offset you enter, morning first and evening second. Twilight is named by how far the sun sits below the horizon: civil at 6°, nautical at 12° and astronomical at 18°. The blue hour runs from 6° to 4° below and the golden hour from 4° below up to 6° above, so golden light starts before sunrise and lasts past sunset. Sunrise and sunset use the standard 0.833° horizon dip for refraction and the sun's disc. The solar position follows the NOAA solar equations for the date at 00:00 UTC, which are usually within a minute or two but neglect your elevation, terrain, atmospheric pressure and temperature. Where the sun never reaches the needed altitude, the row says so instead of inventing a time; at high latitudes that is a real midnight-sun or polar-night result. Daylight saving time is not applied, so use the offset in force on that date. Everything is calculated in the browser with no storage, uploads or network access.