How to calculate age? It's a very common question, and the answer is very simple: just count the days or hours that have passed since your birth date. But you may have a different question in mind: how old is my baby? To answer this question, you need to use another method: count the months or days until your baby's birth date.

The first step in this method is to determine the month and day of birth. If you want to calculate the exact day, you need to know the exact date of birth. But, for most people, the exact date is not so important.