Planetary Hours — Calculation

What Are Planetary Hours

Planetary hours are an ancient system of dividing the day, in which each hour is governed by one of the seven classical planets: the Sun, Moon, Mars, Mercury, Jupiter, Venus, or Saturn. This system was used in Hellenistic astrology, and it is from this tradition that the names of the days of the week in many languages originate.

Why Isn’t a Planetary Hour Equal to 60 Minutes?

The daylight and nighttime periods are each divided into twelve parts, so the duration of a planetary hour varies throughout the year. In summer, daytime hours are longer than 60 minutes, while nighttime hours are shorter; in winter, the opposite is true. They last exactly 60 minutes only on the days of the equinoxes.

How Is the First Hour of the Day Determined?

The first planetary hour begins with sunrise and is governed by the planet that gives its name to the day of the week: the Moon on Monday, Mars on Tuesday, Mercury on Wednesday, and so on. The planets then alternate in the Chaldean order.

What Are Planetary Hours Used For?

Most often, they are used to select the timing of actions: Mercury hour is taken for negotiations, documents, and study; Venus hour for meetings and creativity; Jupiter hour for financial matters; Saturn hour for completing tasks and working with discipline.

This is an auxiliary tool: a planetary hour does not alter the overall picture of transits but only adds nuance to a specific time interval.

Do Planetary Hours Depend on Location?

Yes. The calculation is based on the moments of sunrise and sunset, which differ for each location. Therefore, for an accurate result, you must specify the city where you are currently located, not the city of birth.