Answer:
The problem precession has caused for many schools of astrology is the marking of first day of spring in the North part of Hemisphere which was considered as zero point of the Zodiac which is approximately on March 21.
Over the past 2.5 millennia, this wobbling has moved west side along the ecliptic by 36 degrees, nearly (1/10) of the way around, nearly one whole month. So in Earlier days, those who born during the period March 21 to April 19 consider to be Aries.
Today, the sun is said to be no longer within marking point of the constellation of Aries, whereas sun is actually placed in the constellation of Pisces during the period of March 11 and April 18.