The house system is actually a personalized version of the zodiac which is superimposed over the actual zodiac. This makes for a chart which is uniquely tailored to each person. The placement of the houses is determined by the time of birth along with the place of birth. This is why a person's time of birth is so critical in casting natal charts. 3 below shows a natal chart in combination with transits.
Transits are the positions of the sun, moon and planets charted for any point in time after birth.
Transits are used to forecast a person's future events, to examine the present or to review any event in the past. In a combination chart such as this, the house cusps of the natal chart always predominate. As a result, the natal house cusps are notated outside both wheels. The beginnings of each zodic sign are usually not included in chart notation. By referring to the degree and minute of each sign on the house cusps, the user can easily approximate where the zodiac signs begin and end.