As per Vedic system around 14th of April the first point of Aries falls, in western systems in points out after about 23 days. 2000 years ago people might not have seen the same sky which we see during the time of equinox. Earth shifts back on its axis which appears as if the signs have proceeded.
Also you can say that if one is not born between 15th to 20th of the months their sun sign will shift back to one sign (about 23 degrees i.e. the Ayanamsa or difference of the starting points of Aries in the two systems).
Vedic astrologers give more importance to the Astrological Reading based on the rising sign and on the Moon than on the Sun.
Adding up the 12sun signs of the zodiac Vedic astrology also uses the 27 moon signs or secondary constellations called "Nakshatras".
In Vedic astrology the Vedic system utilizes a set including 16 types of birth charts which are known as "Shodasavargas", and a forecasting system which is called "Vimshottari Dasa", these Vedic system n forecasting systems helps Vedic astrology in tracking events in the birth chart up to a 120 year life period.
Vedic astrology is very strongly connected with religious expansion and awareness, also Vedic astrology put forward 100’s of remedial actions to counter harmful power in the chart.
That way Vedic astrology helps us in knowing that the future time period for us will be favorable or unfavorable, it also has technique to help us in reinforcing ourselves to deal with life events more powerfully.