Time
Exact vs. unknown birth time
A chart can still be calculated in part when the birth time is unknown. ASTRUM does not guess the time; it leaves out details that depend on it.
Brief explanations help you read without specialist knowledge. Astrological terms describe a symbolic method, not scientifically established personality traits.
Of the three inputs a chart needs — date, time, and place — birth time has the largest effect per minute of error. The sky's apparent rotation moves the Ascendant and Midheaven roughly one degree every four minutes of clock time, and house cusps move with them; a planet's zodiac sign, by contrast, only changes over a span of hours to days depending on how fast that planet moves. In other words, a birth certificate that is off by ten minutes can shift the Ascendant by more than two degrees — occasionally enough to change which sign it falls in — while it will essentially never change which sign the Sun or a slow outer planet occupies.
When the exact birth time is unknown, the honest response is to say so plainly rather than guess: a chart built without a reliable time can still show accurate planetary signs and the aspects between them (these do not depend on time of day), but the Ascendant, Midheaven, and house placements cannot be shown reliably and should not be presented as if they were known. Some traditions use a "noon chart" or "sunrise chart" as a stand-in when time is missing — this project's own policy is to be explicit about which parts of a reading are time-dependent rather than to quietly fill a gap with a guess.
See "What is a natal chart?" for how these pieces fit together, and "Astrological houses" for why house cusps specifically are the most time-sensitive part of the picture.
When the exact birth time is unknown, the honest response is to say so plainly rather than guess: a chart built without a reliable time can still show accurate planetary signs and the aspects between them (these do not depend on time of day), but the Ascendant, Midheaven, and house placements cannot be shown reliably and should not be presented as if they were known. Some traditions use a "noon chart" or "sunrise chart" as a stand-in when time is missing — this project's own policy is to be explicit about which parts of a reading are time-dependent rather than to quietly fill a gap with a guess.
See "What is a natal chart?" for how these pieces fit together, and "Astrological houses" for why house cusps specifically are the most time-sensitive part of the picture.