Natal Chart

A natal chart, also called a birth chart, is the foundational document of personal astrology. It is a snapshot of where every major celestial body sat in the sky at the moment a person was born, measured from the location where that birth happened. The chart is conventionally drawn as a circle divided into twelve segments (the houses), with the planets plotted by their ecliptic position around the rim.

A complete natal chart requires three pieces of input: date of birth, time of birth, and place of birth. The date and time fix the planetary positions; the place fixes the rotation of Earth, which determines the rising sign and the houses. Without a birth time, you can still calculate the Sun, Moon, and planet signs (with some uncertainty for the Moon if the birth is near a sign change), but you cannot calculate the ascendant, the midheaven, or any of the houses. Approximately half of what astrologers analyze depends on these.

The natal chart is treated as fixed for life. Although the planets keep moving after you are born, your natal positions never change — they are the snapshot taken at one moment. Subsequent astrology uses your natal chart as a baseline and tracks how the moving sky (transits) interacts with it over time. This is the core operation of a daily personal reading: today's sky × your fixed natal chart = today's personalized influences.

ZODIA's daily readings are built entirely from each user's natal chart, calculated from the date, time, and city of birth they provided at signup. Sun-sign horoscopes use only the Sun's sign at birth. ZODIA uses every major body and every house cusp, which is why two people born on the same day in different cities receive different readings.