The Solar Arc Direction, similar to progression, is based on the idea that there is a symbolic analogy of 1 year = 1 day in the life of a person.

The age of the native is calculated in years, and then multiplied by the mean daily motion of the Sun. The result is added to all planets, axes and houses. The solar arc chart can, like a transit chart, be interpreted in relation to the natal chart (synastry).

The mean daily motion of the Sun (the so-called 'Naibod key') is 0.98564733°.