Understanding How Age Is Counted in Different Cultures

The way people calculate age can vary from culture to culture. This calculator uses the most common age system, which is based on birthdays. In this system, a person’s age increases each year on their birthday.

For example, someone who has lived for 3 years and 11 months is considered 3 years old, and they will turn 4 on their next birthday one month later. Most Western countries follow this method.

Traditional and Cultural Age Systems

However, not all cultures measure age the same way. In some traditions, age is counted by including the current year of life. For instance, a person who is said to be twenty years old might also be described as being in their twenty-first year.

In one traditional Chinese age system, people are considered 1 year old at birth, and their age increases during the Traditional Chinese New Year, not on their actual birthday.
For example, a baby born just one day before the Chinese New Year would be considered 2 years old only two days after birth.

Dealing with Month-End Confusion in Age Calculation

Sometimes, the months and days in age calculations can seem confusing—especially when dates fall near the end of a month.

For instance, we count February 20 to March 20 as one month. But from February 28, 2022, to March 31, 2022, there are two valid ways to calculate:

• If we treat February 28 to March 28 as one month, the result is 1 month and 3 days.
• If both February 28 and March 31 are viewed as the end of their months, the result is simply 1 month.

Both interpretations make sense. Similar cases occur with dates like April 30 to May 31 or May 30 to June 30. These differences arise because months have uneven lengths.

In our calculator, we use the first method, which counts from day to day (e.g., February 28 to March 28).