Why the birth time matters

A date fixes the planets. Only a time fixes the houses — and the difference is the whole chart.

The Earth turns once a day, so the entire house structure rotates a full 360° every twenty-four hours. That is roughly one degree every four minutes. An hour of uncertainty moves the Ascendant about fifteen degrees, which is usually half a sign and often a whole one.

The planets are far more forgiving. The Sun moves about a degree a day, Mercury and Venus a degree or two, the outer planets barely at all. Given only a date, every body except the Moon can still be placed to within a degree or so — which is why a chart without a time is worth drawing, provided nobody pretends it has an Ascendant.

The Moon is the exception. At twelve to fifteen degrees a day it can cross half a sign between midnight and midnight, so a dateless-time chart cannot always say which sign the Moon was in.

This is why every entry here carries a Rodden rating, and why charts without a usable time are drawn with no house cusps and no angles at all. An Ascendant computed from an assumed noon is not an approximation of the real one. It is a different chart.