How a four minute error moves your whole chart

People round their birth time to the nearest quarter hour without thinking. Usually it is harmless. Occasionally it changes the reading completely, and it is worth knowing which situation you are in.

The rate

The ascendant moves roughly one degree every four minutes. Fifteen minutes of error is about four degrees. An hour is about fifteen degrees, half a sign.

When it barely matters

If your ascendant is in the middle of a sign, a fifteen minute error moves it a few degrees and changes almost nothing you would notice. Most charts are in this situation, which is why rounding usually survives.

When it matters enormously

If your ascendant is within a few degrees of a sign boundary, a small error changes the rising sign itself, which changes every house, every house ruler, and the chart ruler. Two readings of the same person become unrecognisable.

The divisional problem

In Vedic astrology it compounds. The navamsa cuts each sign into nine, so a slice is three degrees and twenty minutes wide, about thirteen minutes of birth time. The shashtiamsha cuts it into sixty, where a slice is half a degree, about two minutes. Charts that fine are only meaningful with a recorded time.

What to do

Get the recorded time if it exists. If your ascendant lands near a boundary, say so out loud in any reading, and treat house-dependent conclusions as provisional rather than quietly building on sand.