To determine the position of the planets on that day.
This is an excellent request, as (also known as the Rising Sign or Ascendant ) is the most fundamental pillar of Vedic astrology (Jyotish). Udaya Lagna Calculator
No. Your rising sign is fixed at the first breath. Only progressed systems (used in Western astrology) change Lagna, but traditional Vedic rejects that. To determine the position of the planets on that day