Planetary Hours Calculator

Planetary hours are the medieval unequal hour: sunrise to sunset cut into twelve, then sunset to the next sunrise cut into twelve more, so a summer day hour can run eighty minutes while its night hour runs forty. Give a date, a latitude, a longitude and the UTC offset in force there, and it solves sunrise and sunset from the sun's altitude and lists all twenty-four hours with their Chaldean rulers, beginning with the planet the weekday is named for. A second tab takes a clock time and finds the hour containing it, counting the small hours as part of the previous day because the cycle runs sunrise to sunrise. Inside the polar circles some dates have no sunrise or no sunset, and the page says so instead of inventing an answer. It is history and entertainment, not a prediction.