How to use
- 1
Choose your city; today’s date is filled in for you.
- 2
See sunrise, sunset and the ruler of the day.
- 3
Find the current planetary hour highlighted in the table, or pick another date.
How planetary hours work
The daylight between sunrise and sunset is split into twelve equal hours, and the night until the next sunrise into another twelve. So the hours are only sixty minutes long at the equinoxes; in summer the day hours are longer and the night hours shorter. Each hour is given to one of the seven classical planets in the Chaldean order: Saturn, Jupiter, Mars, Sun, Venus, Mercury, Moon.
Where the weekday names come from
The first hour after sunrise belongs to the ruler of the day: Sun on Sunday, Moon on Monday, Mars on Tuesday, Mercury on Wednesday, Jupiter on Thursday, Venus on Friday, Saturn on Saturday. Running the Chaldean sequence through 24 hours lands exactly on the next day’s ruler, which is how the planetary week, and many weekday names, came about. In traditional practice, people chose an hour whose planet suited the activity.
Frequently asked questions
When does the planetary day start?
At sunrise, not at midnight. Between midnight and sunrise you are still in the night hours of the previous planetary day, which the banner accounts for.
Why are the hours not 60 minutes long?
They are “unequal hours”: one twelfth of the actual daylight or night, so their length changes with the season and latitude.
What about places with midnight sun or polar night?
If the Sun does not rise or set on that date, planetary hours are not defined and the tool says so.