How it works
Three details, and your chart is worked out.
Everything in Third House starts from your chart, worked out exactly from the moment you were born, so here’s what happens to it.
1. You give three details
Your birth date, time and place. You pick the place from a list, so we know the exact spot and the time zone that applied that day. Time zones have shifted over the years, often capriciously, and the wrong one makes a chart wrong by hours.
If you don’t know your birth time
Say so instead of guessing. We still put every planet in its sign, and we just don’t show houses or a rising sign, because those are unknowable without the time. A guessed time gives a chart that looks sure of itself and is quietly wrong. If you find your birth certificate later, correct the time and the chart gets worked out again.
2. The chart is worked out
The planets’ positions come from the same astronomy engine professional astrology software uses, checked against NASA. From them, our engine works out everything your tradition requires: houses and aspects, Vedic planetary periods, the Chinese four pillars, and the rest. Each tradition’s rules, from its classical texts, are built into the engine itself.
Change a birth detail and the chart is worked out again from scratch. You never see yesterday’s sky.
3. Mercury reads it
Mercury is an AI astrologer that gets your finished chart before you say a word. It never asks your sign and never does the math itself, it just interprets what the engine worked out. Ask it anything, like why you keep repeating a pattern, what’s going on for you right now, or whether you and someone else are a disaster waiting to happen.
Mercury reads moments, so today and, on a paid plan, any date you name. It isn’t given a timeline of when things begin, peak or end on any plan, and it won’t guess one. The timing reports are built from those dates.
On Premium, Mercury reads all four traditions and can switch between them mid-conversation without losing anything you’ve told it. Ask your Vedic chart and your Western one the same question and you get two distinct answers, because they’re two genuinely different charts.
Why not just ask an AI chatbot?
You can chat about astrology with any AI chatbot, usually for free, so we tested them. The full write-up has the method and every result.
We tested it
We asked AI models for readings, and checked every claim against the chart.
16 people, three AI models of different sizes, each asked the way a person asks: birth details typed in, “can you give me a reading?” Every placement, house and aspect a reading stated was checked against the real chart.
One wrong placement isn’t a small slip: the reading built on it is about someone else. The mid-size model mostly declined to name placements, so it had few to check.
“Your Moon’s position may be off. On 14 March 1985, the Moon was approaching its last-quarter phase, which by my reckoning puts it around 20–22° Sagittarius, not 3° Capricorn. (The listed Moon is almost exactly on your Neptune, which suggests a data mix-up.)”
The most capable model, asked for a reading, to someone whose pasted chart was correct. The Moon was at 3°46′ Capricorn.
Given the correct chart to read from, the same models got 1 of 164 claims wrong, and that one was the model above overruling it. A reading is only as good as the chart under it. Asked to work the chart out themselves, here is how often each got it right, one dot per person. Even the most capable got worse outside Western astrology:
Mercury never works a chart out as it goes. Every one of these is computed for your chart before it says a word, and checked against NASA’s JPL ephemeris.
Median, per chart. The smaller model answered in seconds by declining 15 of 16.
We tested 16 births from 1955 to 2010 on six continents, including a birth on the morning the clocks changed, a leap day and a sign cusp. Mercury’s figures are its own replies, a different set of questions checked the same way.
Chatbots are honestly bad at the math. Ask one for a reading and it guesses your chart as it goes, and the further you get from Western astrology the worse the guesses get, which is how you end up with a reading about a Moon you don’t have. Here’s what Mercury does differently.
It does the math first.
Your chart is worked out exactly before Mercury says a word, and Mercury reads from it faithfully. It never works a chart out mid-conversation, not even from birth details you type in.
Every tradition, just as exact.
Chatbots get shakier in every tradition beyond Western. The best one we tested got every Western chart right, then got the Vedic rising sign wrong 1 time in 16, the Hellenistic Lot of Fortune wrong 1 time in 8 and the Chinese four pillars wrong 1 time in 4. Smaller models did worse in every tradition. Mercury works out all four exactly, and reads each by its own rules. What each tradition works out.
The rules are built in.
Each tradition’s rules, drawn from its canonical texts, are part of the engine itself: Vedic planetary periods, the Hellenistic day and night charts, the Chinese four pillars. Mercury doesn’t have to remember them, so it can’t misremember them.
It remembers you.
On Premium and Plus, Mercury remembers what you tell it from one conversation to the next: the new job, the move, how you like to be read. You can see and delete everything it remembers in Settings. Your chart and the people you’ve saved are always there, on every plan.
It doesn’t make things up.
It won’t invent a date or promise you a certainty, and if something hasn’t been worked out, it’ll tell you.
It reads the real sky.
Today’s planets, worked out against your chart. On a paid plan, the sky on any date you name, from your birth on.
Two people, compared each tradition’s way.
Each tradition compares two charts in its own way, and so does Mercury. It’s not one method with four names on it.
Checked against NASA.
Every planet position Mercury reads is checked against NASA’s own data. For anyone born since 1900, no position is off by as much as one arcsecond, a sliver sixty times finer than any chart can show.
4. Reports, when you want it in writing
A report is a long, structured PDF written from your chart in one of the four traditions. There are five kinds:
- Natal Deep-Dive. Who you are: your birth chart, read in full. It’s about the pattern you were born with, not about timing.
- Compatibility. Two charts read against each other, by the method their tradition uses: where you meet easily, where you grind, and what each of you is asking for.
- Look-Back. Up to 10 years behind you, read in chapters and dated: a decade, a span of years you choose, or a single year.
- Right Now. What’s active in your life now, dated: what ended in the last month, what’s running, and what arrives in the next three months.
- Year Ahead. The next 12 months, dated: when each influence arrives, when it peaks and when it passes.
Each one includes the figures it’s working from, and the three timing reports include the dates too, so you can check the reading against the chart instead of taking it on faith.
A report is written once.
It keeps the chart it was written from for good, so correcting or deleting a chart later never breaks a report you already have, and it never rewrites one either. So check your details before you order, which is exactly why the order page shows them to you.
Charts other than your own
You can save more than your own chart, like a partner, a parent or a child. A free account holds one chart, yours; Premium holds 2, you and one other person, and Mercury compares the two of you in Western; Plus holds 6 and compares any two in every tradition. A compatibility report doesn’t need a saved chart at all, since any plan can type the other person’s details in when ordering.
You can correct a saved chart’s time or place at any point before a report has been written from it. You can’t change its date, though, because a different date is a different person, and that’s what adding a second chart is for.