Planetary Hours Calculator

Planetary hours are an ancient time-division system dating back to Babylonian astrology (circa 7th century BCE) and later refined in Hellenistic astrology. Unlike our modern 60-minute hours, planetary hours divide the period of daylight into 12 equal segments and the period of darkness into another 12 segments.

Each hour is ruled by one of the seven classical “planets” visible to the naked eye: Saturn, Jupiter, Mars, the Sun, Venus, Mercury, and the Moon. They cycle in the Chaldean order — from the slowest-moving celestial body (Saturn) to the fastest (Moon).

The first hour after sunrise is ruled by the planet that governs that day of the week — which is why Sunday begins with the Sun, Monday with the Moon, Tuesday with Mars (Mardi in French), and so on. This system is preserved in the names of weekdays across many languages.

In traditional practice, planetary hours were used to elect auspicious times for activities: the Hour of Venus for love, Jupiter for prosperity, Mars for courage, and Mercury for communication.