A natal chart or birth chart is a map of the sky including the positions of the planets for the time that you were born. Where you are born has an impact on what is seen in the sky, e.g., if two people were born on the same day and at the same time but in a different city and country, what is seen overhead would be different. This would mean that their natal charts showing planetary placements would be different from each other. So, to cast a birth chart, birth date, time and place are all needed.