Tools

Planetary Hours Calculator

Divide any day and night into the twenty four planetary hours and find the ruler of each.

Set the day

Enter local clock times from an almanac, or estimate them below.

Estimate sunrise and sunset

Decimal degrees. North and east are positive, south and west negative. The time zone is taken from this device. Change the hours from UTC if you are reckoning for a place in another zone.

Planetary hours

Choose a date and calculate

The ruler of the day and the planet of the present hour will appear here.

How the hours are reckoned

Planetary hours are not sixty minute hours. The time from sunrise to sunset is divided into twelve equal parts, which are the hours of the day. The time from sunset to the following sunrise is divided into twelve more, the hours of the night. In summer the day hours are long and the night hours short. In winter it is the other way about.

The first hour of the day, beginning at sunrise, belongs to the planet that rules the day: the Sun on Sunday, the Moon on Monday, Mars on Tuesday, Mercury on Wednesday, Jupiter on Thursday, Venus on Friday and Saturn on Saturday. The hours that follow are given to the planets in the Chaldean order, which runs Saturn, Jupiter, Mars, Sun, Venus, Mercury, Moon and then begins again. The sequence continues without a break through the night, and the first hour of the next day falls to the ruler of that day.

Note that the planetary day begins at sunrise and not at midnight. The hours before dawn belong to the night of the day before.

Working it by hand

  1. Find the times of sunrise and sunset for your place and date, and of sunrise on the following day.
  2. Count the minutes from sunrise to sunset and divide by twelve. That is the length of one hour of the day.
  3. Count the minutes from sunset to the next sunrise and divide by twelve. That is the length of one hour of the night.
  4. Write out the twenty four hours with their starting times.
  5. Give the first hour to the ruler of the day and continue in Chaldean order.

Using the hours

The traditional rule is to begin a piece of work in the hour of the planet that governs it, and for preference on that planet's day. Study and writing are begun in an hour of Mercury, matters of friendship in an hour of Venus, tasks needing endurance in an hour of Saturn. Each planet rules three or four hours in every day, so there is always a suitable time.

You may find, as many do, that the chief benefit is attention. To stop and ask what kind of hour it is, and what belongs to it, is already a small act of recollection. For the wider subject see planetary magick.

A note on accuracy

The estimate uses a standard astronomical approximation for sunrise and sunset and is usually correct to within two or three minutes at moderate latitudes. It takes no account of hills, buildings or unusual atmospheric conditions. Near the polar circles in midsummer and midwinter the Sun may not rise or set at all, and the system of planetary hours cannot then be applied. For exact times use a printed almanac for your location and enter them by hand.