When you approach astrologer to make horoscope for accuracy the astrologer need your date of birth, time of birth and place of birth. Sometimes you don’t have correct time of birth. In that case the prediction accuracy gets affected. Because in horoscope there are major period (mahadasha) and sub periods to interpret what will happen and when.
These period and sub period are as date, month and year format. If you’re correct birth time is 10:00 am and you give an estimated 10:15 or 10:20 then these 15-20 minutes affect your period and sub period by approx. one month. The more accuracy in the date and time will give more accurate prediction an astrologer can interpret. If you want me to analyze your horoscope, give me your complete birth details. The form is already given above.
Birth chart is dependent upon your date, time and longitude, latitude. There is a simple rule that if you have mercury in 7th house of horoscope you will have marriage before the age of 20. This rule always work. But no one can tell his / her birth time with accuracy because a baby’s birth takes time & the moment the baby first time cry that should be taken as time of birth