See planetary hours personalized to YOUR chart
Create a free account to see which planetary hours align with your natal placements and get personalized timing guidance.
What are planetary hours?
Planetary hours are an ancient timing system that divides each day into 24 unequal segments, each ruled by one of the seven classical planets. The system follows the Chaldean order — Saturn, Jupiter, Mars, Sun, Venus, Mercury, Moon — cycling through all 24 hours from sunrise to the next sunrise. The planet that rules the first hour after sunrise also names the day of the week.
Unlike clock hours, planetary hours are based on local sunrise and sunset. The 12 day hours divide the period between sunrise and sunset equally, and the 12 night hours divide sunset to the next sunrise. This means day hours are longer in summer and shorter in winter. For the full history and calculation method, see our complete guide to planetary hours.
What each planetary hour means
Hour of the Sun
Visibility and leadership — step into the spotlight. Learn more →
Hour of the Moon
Nurturing and home — care for family, cook, rest, or take a short trip. Learn more →
Hour of Mars
Action and drive — tackle hard tasks, exercise, compete. Learn more →
Hour of Mercury
Communication and commerce — send messages, make plans. Learn more →
Hour of Jupiter
Abundance and wisdom — seek opportunities, travel, learn, or teach. Learn more →
Hour of Venus
Pleasure and connection — beautify, socialize, reconcile. Learn more →
Hour of Saturn
Discipline and structure — organize, do focused work, plan long-term. Learn more →
How this calculator works
This calculator computes sunrise and sunset times for your location using the Jean Meeus solar position algorithm, then divides the resulting daylight and nighttime into 12 equal planetary hours each. The first hour is assigned to the day ruler, and subsequent hours follow the Chaldean sequence.
All computation happens in your browser — no server requests are needed after the initial page load. The current hour updates every second with a live countdown. For a deeper explanation of the mathematics and history, read our guide to planetary hours and days of the week.
More Free Tools
Frequently Asked Questions
What are planetary hours?
Planetary hours are an ancient timing system that divides each day into 24 segments, each ruled by one of the seven classical planets (Sun, Moon, Mars, Mercury, Jupiter, Venus, Saturn). The sequence follows the Chaldean order, starting from the planet that rules the day. Day hours run from sunrise to sunset and night hours from sunset to the next sunrise, so their length changes with the seasons.
How are planetary hours calculated?
The time between sunrise and sunset is divided into 12 equal parts (day hours), and the time between sunset and the next sunrise is divided into 12 equal parts (night hours). In summer, day hours are longer than 60 minutes and night hours are shorter; in winter, it reverses. The first day hour is always ruled by the planet that rules the day — Sun on Sunday, Moon on Monday, Mars on Tuesday, and so on — and subsequent hours follow the Chaldean order.
What is the Chaldean order?
The Chaldean order is Saturn, Jupiter, Mars, Sun, Venus, Mercury, Moon — arranged by orbital period from longest to shortest. This ordering was established by Babylonian astronomers based on each planet's sidereal cycle and determines which planet rules each successive hour throughout the day.
Is the planetary day or planetary hour more important?
Traditional electional astrologers treat both as significant, but the planetary hour provides finer timing. The planetary day sets the overall tone, while the hour pinpoints the best window within that day. For maximum effect, choose an activity when both the day and hour are ruled by the same planet — for example, doing Jupiter-related work (studying, legal matters, travel) during a Jupiter hour on Thursday.
Why does this calculator need my location?
Planetary hours are based on local sunrise and sunset times, which depend on your geographic latitude and longitude. Two people in different cities will have different planetary hour times on the same day because their sunrise and sunset times differ. The calculator uses your location to compute accurate local times.
Do planetary hours change with the seasons?
Yes. Because planetary hours divide the actual daylight and nighttime into 12 equal parts each, day hours are longer in summer (when days are long) and shorter in winter. Night hours are the opposite. Near the equinoxes, day and night hours are close to 60 minutes each. At extreme latitudes in summer or winter, the difference can be dramatic.