Sundial House

Your Big Three

Sun, Moon and Rising — calculated from tropical zodiac dates and standard astronomical algorithms, with the limits of each one stated up front.

What each placement needs

  • Sun sign — birth date only.
  • Moon sign — birth date, birth time, and birth city. The city supplies the timezone, without which a clock time can't be pinned to a real moment.
  • Rising sign — birth date, exact birth time, and birth city.

Fill in as much as you have. You'll get every placement your inputs actually support, and nothing that they don't.

Required. Gives you your Sun sign.

Optional. Local clock time at the place you were born. Needed for your Moon and Rising signs, together with a birth city.

Optional. Needed for both your Moon and Rising signs — a birth time can't be placed on the sky without a timezone.

How accurate this is

Sun sign

The Sun sign comes from standard tropical zodiac date ranges, which is reliable for almost everyone. The exception is being born within about a day of a boundary date — the exact moment the Sun changes sign shifts slightly from year to year, so a cusp birthday can land on either side.

Moon sign

The Moon sign uses the Meeus low-precision lunar algorithm — a standard, well-documented ephemeris approximation, not a professional-grade ephemeris like Swiss Ephemeris. It's reliable for the vast majority of birth times. The Moon changes sign roughly every two and a half days, so if your birth time falls very close to a sign-change moment there's a small chance of landing on the adjacent sign.

Rising sign

This is the placement most sensitive to precision — please double-check that your birth time is exact if you can. The Ascendant moves through a full zodiac sign in about two hours, so an error of even fifteen minutes can genuinely produce a different sign, not just a slightly imprecise degree.

Birth locations

Birth locations come from the GeoNames cities5000 dataset — roughly 69,000 places worldwide with a population of 5,000 or more, plus regional administrative capitals, each with its coordinates and IANA timezone. There is no geocoding service behind this, so very small villages and hamlets may still be missing; if yours is, we'll say so rather than guess with a nearby point.

City coordinates and timezones from GeoNames, licensed under CC BY 4.0. geonames.org