They don't. That's Sun Sign astrology found in newspapers and magazines. Sun
Sign astrology forecast take the sign the Sun was in when you were born and set
up a solar chart based only on the Sun. This puts the Sun Sign on the Ascendant
and all the Houses (areas of life) can be looked at for planetary activity.
Since the Sun is the most important influence on all of us - think of its size
and power in relation to other planets not to mention sunspots and solar fare
activity - such forecasts can give useful information.
Your unique Full Birth Chart is exactly that - unique. No one else on the
planet shares your characteristics, DNA, attributes, history. The Full
Birth Chart is set for the time, date and place of your birth with 10 planets
plus other important points in various relationships with each other through
specific houses.
Every Full Birth Chart is different, just like a snowflake or a fingerprint.
That's why twins turn out differently if there's a minute or so between their
births.
Curious ? Order your own Sky Within report - it will
open your eyes to yourself and your as yet untapped potential.