What are planetary hours?

Planetary hours are an ancient system that divides the time between sunrise and sunset into twelve 'hours', and the night into twelve more, each ruled by one of the seven classical planets — a way of giving every part of the day a character.

Are planetary hours 60 minutes long?

Not exactly. They stretch and shrink with the seasons. Daytime hours are longer in summer and shorter in winter, because the system splits actual daylight into twelve equal parts rather than clock-hours.

How do I calculate planetary hours?

Take the real sunrise and sunset for your date and location, divide the daylight between them into twelve equal parts, and give the first part to the planet that rules that weekday. The remaining hours follow the Chaldean order: Saturn, Jupiter, Mars, Sun, Venus, Mercury, Moon, repeating.

Are planetary hours the same everywhere?

No. They depend entirely on your latitude and longitude, because they are built from local sunrise and sunset. The hours in London on a given day are a different length, and start at a different clock time, than the hours in Manila.

Planetary Hours: The Oldest Way to Time Your Day

Planetary hours split day and night into segments ruled by the seven classical planets. What they are, how to calculate them yourself, and how to use them.

Long before clocks, people told time by the sky and gave each part of the day its own character. Planetary hours are one of the oldest of these systems, and they are still used in astrology and ritual today.

The idea in one sentence

Planetary hours divide the daylight into twelve parts and the night into twelve more, and hand each part to one of the seven classical planets: the Sun, Moon, Mercury, Venus, Mars, Jupiter and Saturn. Every hour has a ruler, and that ruler colours the hour’s traditional character.

Why the hours aren’t 60 minutes

A planetary “hour” is not a clock hour. The system takes the actual time between sunrise and sunset and divides it into twelve equal pieces. In summer, when days are long, the daytime hours run well past sixty minutes; in winter they shrink. The night’s twelve hours make up the difference, so the two sets are always uneven except near an equinox.

That has a consequence worth stating plainly: planetary hours depend on where you are and what date it is. Real sunrise and sunset at your coordinates, not a fixed schedule. The hours for London and the hours for Manila on the same day are different lengths and start at different times. Any table that gives you “the planetary hours” without asking your location is giving you somebody else’s.

The order of the planets

The first hour after sunrise belongs to the planet that rules that day of the week: the Sun on Sunday, the Moon on Monday, Mars on Tuesday, Mercury on Wednesday, Jupiter on Thursday, Venus on Friday, Saturn on Saturday.

From there the hours follow the Chaldean order, an old sequence based on how fast each planet appears to move across the sky, from slowest to fastest: Saturn, Jupiter, Mars, Sun, Venus, Mercury, Moon. Reach the end and you start again.

How to calculate them yourself

Four steps, and the arithmetic is the whole method.

Get the real sunrise and sunset for your date and location.
Divide the daylight by twelve. That gives you the length of one daytime hour.
Assign the first hour to the weekday’s ruler, starting at sunrise.
Walk the Chaldean order for the remaining eleven, then do the same for the night using sunset to the next sunrise.

Worked through, on a hypothetical Sunday with sunrise at 6:00 AM and sunset at 8:00 PM. That is fourteen hours of daylight, so each planetary hour runs 70 minutes. Sunday’s ruler is the Sun, so the first hour is the Sun’s, and the Chaldean order takes over from there:

#	Starts	Ruler
1	6:00 AM	Sun
2	7:10 AM	Venus
3	8:20 AM	Mercury
4	9:30 AM	Moon
5	10:40 AM	Saturn
6	11:50 AM	Jupiter
7	1:00 PM	Mars
8	2:10 PM	Sun
9	3:20 PM	Venus
10	4:30 PM	Mercury
11	5:40 PM	Moon
12	6:50 PM	Saturn

The twelfth hour ends at 8:00 PM, exactly at sunset, and the night’s twelve hours pick up the sequence from there.

Now follow that loop all the way around. Twenty-four hours after the Sun’s hour opened Sunday, the sequence lands on the Moon — and the Moon rules Monday. Keep going and every twenty-fifth hour hands you the next weekday’s ruler, in the order we still use. The names of the days of the week fall out of this table. That is the same logic preserved in French mardi for Mars and mercredi for Mercury, and in English through Norse equivalents.

What each ruler is traditionally “for”

People who work with planetary hours often pick an hour whose ruler suits the task at hand, as a ritual for focus rather than a promise of results:

Sun — vitality, confidence, stepping into the light.
Moon — home, rest, tending to feelings.
Mercury — messages, learning, conversations.
Venus — love, connection, beauty.
Mars — drive, courage, hard effort.
Jupiter — growth, study, opportunity.
Saturn — discipline, planning, commitment.

None of this predicts an outcome. It is a way of noticing the rhythm of your day and choosing a moment deliberately, which is a very old habit of paying attention.

Where this sits in the rest of astrology

Planetary hours are a timing system, not a chart-reading one. They describe the quality of a moment for everyone in your location, rather than anything personal to you — which makes them the natural companion to your birth chart rather than a substitute. Your birth chart is one frozen moment; planetary hours are the moments still arriving. If you want the personal layer instead, that starts with your Big Three.

Using them today

You do not need a sunrise table and a pen. In MysticAlmanac, the day’s planetary hours are computed from the real sunrise and sunset at your location and mapped to the parts of your life: a good hour for a hard conversation, a good hour to rest. The oldest timing system in the book takes about ten seconds to read.

Pick an hour. Notice what it is traditionally for. Then use it, and see whether the shape of your day changes.