Planetary hours
Twelve unequal hours of daylight, twelve of night, each with its classical ruler.
London, United Kingdom
Thursday, August 6, 2026
Showing London by default. Search for your own city to recalculate.
Ruler of the day
Jupiter
Sunrise
05:32 AM
Sunset
08:42 PM
Daytime hour / Night hour
76 min / 44 min
Hours of daylight
| Hour | Ruler | Begins | Ends |
|---|---|---|---|
| 1 |  Jupiter | 05:32 AM | 06:48 AM |
| 2 |  Mars | 06:48 AM | 08:04 AM |
| 3 |  Sun | 08:04 AM | 09:20 AM |
| 4 |  Venus | 09:20 AM | 10:36 AM |
| 5 |  Mercury | 10:36 AM | 11:51 AM |
| 6 |  Moon | 11:51 AM | 01:07 PM |
| 7 |  Saturn | 01:07 PM | 02:23 PM |
| 8 | Jupiter | 02:23 PM | 03:39 PM |
| 9 | Mars | 03:39 PM | 04:55 PM |
| 10 | Sun | 04:55 PM | 06:11 PM |
| 11 | Venus | 06:11 PM | 07:26 PM |
| 12 | Mercury | 07:26 PM | 08:42 PM |
Hours of night
| Hour | Ruler | Begins | Ends |
|---|---|---|---|
| 1 | Moon | 08:42 PM | 09:27 PM |
| 2 | Saturn | 09:27 PM | 10:11 PM |
| 3 | Jupiter | 10:11 PM | 10:55 PM |
| 4 | Mars | 10:55 PM | 11:39 PM |
| 5 | Sun | 11:39 PM | 12:24 AM |
| 6 | Venus | 12:24 AM | 01:08 AM |
| 7 | Mercury | 01:08 AM | 01:52 AM |
| 8 | Moon | 01:52 AM | 02:37 AM |
| 9 | Saturn | 02:37 AM | 03:21 AM |
| 10 | Jupiter | 03:21 AM | 04:05 AM |
| 11 | Mars | 04:05 AM | 04:50 AM |
| 12 | Sun | 04:50 AM | 05:34 AM |
All times in the local zone of the place shown.
A planetary hour is a twelfth of the daylight or a twelfth of the night, which means it is almost never sixty minutes long. In June a daytime hour at this latitude runs well over an hour while its night hour runs short, and the two meet at sixty minutes only around the equinoxes. That is the whole idea: the hour follows the Sun rather than the clock.
The first hour after sunrise belongs to the ruler of the weekday, and every hour after it steps down the Chaldean order, from the slowest visible planet to the fastest: Saturn, Jupiter, Mars, Sun, Venus, Mercury, Moon. Walk twenty-four of those steps and you land on the next weekday's ruler, which is why Saturday follows Friday in the planets as well as in the calendar. The names of the days are a fossil of this table.
The planetary day runs from sunrise to sunrise, not from midnight to midnight, so two in the morning still belongs to the day before. Electional astrology uses the hour as a fine layer once the day itself has been chosen: an hour describes a condition of the moment, not a result. Sunrise and sunset here are computed from Swiss Ephemeris for the exact coordinates you pick.
Frequently Asked Questions
Why are the hours not sixty minutes long?
Because they divide the actual daylight into twelve and the actual night into twelve. In summer a daytime hour runs long and a night hour short; near an equinox both land close to sixty minutes.
When does the planetary day begin?
At sunrise, not at midnight. The hours between midnight and dawn belong to the day before, so they carry the previous weekday's ruler.
How were planetary hours used?
As a fine timing layer after the day had been chosen: a Mercury hour for letters and negotiation, a Venus hour for reconciliation, a Saturn hour for what needs patience. Tradition treats the hour as a condition of the moment rather than a promise about the outcome.
Does this work inside the Arctic Circle?
Only on dates when the Sun both rises and sets. When it stays up or stays down for a whole date, there is nothing to divide into twelve and the tool says so instead of inventing hours.