Planetary Hours Calculator

In traditional astrology each hour of the day is ruled by one of the seven classical planets. Daytime, from sunrise to sunset, is divided into 12 planetary hours and night-time into another 12, so the hours are longer or shorter than 60 minutes depending on the season. Choose a date and place to see which planet rules each hour.

Why the days of the week are named after planets

The Chaldean order lists the seven classical planets from slowest to fastest: Saturn, Jupiter, Mars, Sun, Venus, Mercury, Moon. When the hours follow this order for 24 hours, the first hour of the next day moves three places along, giving the sequence Sun, Moon, Mars, Mercury, Jupiter, Venus, Saturn: Sunday, Monday, Tuesday (Tiw, the Norse Mars), Wednesday (Woden, linked with Mercury), Thursday (Thor, linked with Jupiter), Friday (Frigg, linked with Venus) and Saturday. The same order gives the weekday names in Thai and many other languages.