Transit Chart Calculator
Your Sun sign and an approximate Moon sign for any date, computed in your browser. Nothing else is guessed.
Pick a date, such as your birthday, and this tool works out the Sun sign and the Moon sign for that date, plus the signs for today. The Sun sign is computed from the Sun real longitude. The Moon sign is computed from a short Moon longitude series and is labelled approximate, because it is good to about 0.3 degrees. Astrology is not science, and this tool is for fun. What it will not do is invent planet positions.
Honest limits: what this tool does not compute
It does not compute Mercury, Venus, Mars, Jupiter, Saturn, Uranus, Neptune or Pluto. It does not compute your rising sign, your houses, or aspects between planets. Those need a full ephemeris and, for the rising sign, an exact birth time and place. A page that shows them from a birth date alone is making them up. This tool shows the Sun and the Moon only, and says which is approximate.
All sums run in your browser. Nothing you type is sent to a server or saved.
How the two signs are worked out
The Sun sign comes from the Sun longitude on the date you pick. The tool takes the days since 1 January 2000, works out the Sun mean longitude and mean anomaly, then adds the equation of centre, which is the correction for Earth oval orbit. The result is good to about 0.01 degrees, so the sign is solid except within minutes of a sign change. The zodiac sign is the 30 degree slice that longitude falls in, starting with Aries at 0 degrees.
The Moon sign comes from a short series for the Moon longitude: its mean longitude plus the largest periodic terms, which are the corrections for the Moon oval orbit and the Sun pull on it. That series is good to about 0.3 degrees, which is why the Moon sign is labelled approximate on the page. The Moon crosses a whole sign in about two and a half days, so it is right except very near a sign change. The tool says so when the Moon sits within one degree of a change.
Frequently Asked Questions
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