What Are Planetary Hours

Planetary hours are one of the oldest systems of dividing time, handed down to us from ancient astrology. They are often mentioned in connection with magic, religious practices and calendars, but few people explain how the system actually works. Let's sort it out step by step.

What is a planetary hour?

A planetary hour is not an hour in the usual sense of the word. Unlike a regular hour, which always lasts 60 minutes, a planetary hour is one twelfth of daylight or of the night.

• Day hours: daylight from sunrise to sunset is divided into 12 equal parts.
• Night hours: the night from sunset to the next sunrise is also divided into 12 equal parts.

That makes 24 planetary hours in every day, but their length changes through the year: in summer the day hours are longer than the night hours, in winter — the other way around. Only at the equator are they almost always close to 60 minutes.

Each hour is associated with one of the seven classical planets: Saturn, Jupiter, Mars, the Sun, Venus, Mercury and the Moon.

How planetary hours are calculated

The formula is simple:

1. Take the sunrise and sunset times for a specific place.
2. Divide the length of daylight by 12 — that gives the day hours.
3. Divide the length of the night (from sunset to the next sunrise) by 12 — that gives the night hours.

This is why, at the same moment, planetary hours differ from city to city: they depend on latitude, longitude and the date. At polar latitudes, where the Sun does not set or does not rise for days, a special mode is used — polar day or polar night.

The Chaldean order and rulers of the day

The hours follow one another in the Chaldean order: Saturn → Jupiter → Mars → Sun → Venus → Mercury → Moon, after which the sequence repeats.

The first daylight hour always belongs to the planet that rules the day of the week:

This, by the way, is where the names of the weekdays come from in many languages: Sunday is the day of the Sun, Monday is the day of the Moon, Saturday is the day of Saturn.

How to use planetary hours on lunar.day

On the planetary hours page for your city you will find:

• The current hour — which planet rules it right now and how much time has already passed.
• The rulers of the day and night — the planets that open the day and night sequences.
• A table of all 24 hours — with the start and end of each hour in local time.
• Sunrise, sunset and next sunrise times for your date.

The data is calculated from the precise astronomical coordinates of your city, and the times are adjusted to your time zone.

Planetary hours are a tradition, not a science

It is important to understand: planetary hours are not a scientific method of timekeeping. It is a traditional system with ancient astrological and religious roots. The calculations themselves use precise astronomical data, but assigning ruler planets to the hours is a convention of tradition. On lunar.day we honestly mark this section as esoteric: use it as cultural heritage and a curious tool, not as a guide for making decisions.