Some cultures count age differently. In certain traditions, age includes the current year, meaning a 20-year-old could also be referred to as being in their 21st year of life. In a traditional Chinese age system, babies are born at age 1, and their age increases with the Chinese New Year instead of their birthday. For instance, a baby born a day before the New Year would be 2 days old but considered 2 years old after the holiday.

In some cases, age calculations involving months and days may seem confusing, especially when the start date falls at the end of a month. For example, from Feb. 20 to Mar. 20 is clearly one month, but from Feb. 28 to Mar. 31, there are two valid ways to calculate:

1. Counting Feb. 28 to Mar. 28 as one month, the result would be one month and 3 days.
2. Considering both Feb. 28 and Mar. 31 as month-end dates, the result would be exactly one month.

Since months have different lengths, this variation can also occur with dates like Apr. 30 to May 31 or May 30 to June 30. This calculator follows the first method, ensuring a consistent approach.