Astrology

You read charts, yours or other people's, and a reading is only as sound as the chart under it, down to the time zone in force where the birth took place. Astrology gathers calculators that work from the ephemeris, for a birth chart, transits, a solar return, synastry and the retrograde dates. They are free, need no account, and forget your birth details once the chart is cast.

The birth chart copes with an unknown birth time

The birth chart calculator asks for a date, a time and a city. The city fixes the coordinates and the historical time zone, the usual culprit when two charts of the same person disagree. Back come the wheel, every planet with its sign, degree and house, and every aspect with its orb.

Tick the unknown-time box and the tool sweeps the whole day at your birth place instead of inventing an hour, listing the rising sign as spans. When the birth town has namesakes, the latitude and longitude finder tells them apart by country, population and time zone.

Transits come with the exact dates ahead

The transit chart calculator answers "what is happening for me right now" against your birth chart, for now or for a future date: every current contact with its orb and the house it falls in, then a timeline of exact contacts over the next 30 or 90 days. I would read the timeline first, since it shows a Saturn contact exact in March, July and December as one transit in three passes.

A solar return is an instant, and the place decides its houses

The solar return chart calculator finds the minute the Sun comes back to its exact birth degree, often the day before or after your birthday, and casts the chart for that instant. Add up to five places: the instant stays the same, and each place gets its own ascendant and Midheaven, side by side.

Synastry reads compatibility contact by contact, with no score

The synastry calculator reads each birth in its own city's time zone, draws one chart inside the other, and ranks the contacts by how close they are rather than by whether tradition calls them good. It can also fold the pair into a composite or a Davison chart. There is no compatibility percentage, and I think that is the right call: a score would have to weigh a Venus trine against a Saturn square on a scale no method agrees on.

The retrograde dates leave with you as a file or a calendar

The planet retrograde calendar needs only a year. It lists every retrograde period from Mercury to Pluto, station to station, in UTC; the table downloads as a file, and the year comes as a calendar you can subscribe to. The equinox and solstice dates give the four instants of the year to the minute, which matters because the tropical zodiac these charts use is measured from the equinox.

Questions

Is this astrology calculator free?

Yes. There is no account or e-mail to give, and your birth details are forgotten once the chart is computed.

Do I need my exact birth time?

Not for the Sun, the Moon, the planets and their aspects. Without it you lose the ascendant, the Midheaven and the houses, in a birth chart and in a solar return chart alike.

Why does my chart differ from another astrology program?

Check the house system, then the time zone applied to the birth time, then whether the other program assumed noon.