This age calculator uses 2 similar but slightly different methods to calculate age. One method is used to give age in years, months and days, and also months and days. The other method is used to very precisely calculate age in total days only.

When calculating age to the detailed level of days it’s important to remember that not all months have the same number of days. Also, while a year has 365 days, a leap year has 366 days.

When you calculate age in terms that include years, this calculator provides the answer in common terms. For example, a teenager might say he is 15 years old rather than saying he’s 12 normal years old plus 3 leap years old. This age calculator uses the same assumption — although we know years may have different lengths, we generalize between regular years and leap years, and call them equal.

The same is true for months. If a baby is 7 months old, the parents would not say she is 4 months that are 31 days long, plus 2 months that are 30 days long, plus 1 month that is 28 days long. We typically generalize across months of different lengths, and count them all equal as general months.