Three pieces of important information are essential for an accurate astrological interpretation. Birth date. Birth time (we may ask for Time Zone). Birth place.
This information is critical, because this is the basis of the birth map. A birth map, commonly known as a birth chart, shows the positions of the planets at the time of birth. This map is drawn up from the perspective of the exact location and time of where you were born.
If we look into the sky each hour on a clear night, the stars would be in different positions, right?
If we look every 10 minutes, we notice the moon changing location. It may also be changing zodiac signs from, say, Virgo to Libra. These alterations can be enough to skew the birth map with symbolism that does not have meaning for you.
Since an interpretation focuses on you, we take it seriously that the birth time is a good one. Good input, good output.
This important information must be trustworthy
Preferably, the birth time comes from a reliable, documented source. Hospital records, baby book, birth certificate, birth notices and family bible are some places which can list the birth time. If this is unavailable, read about Rectification of Birth Time for details on how to obtain a birth time.