Age can be calculated differently depending on cultural traditions. This calculator follows the most common method, used in most Western countries, where a person’s age increases on their birthday. For example, someone who has lived for 3 years and 11 months is considered 3 years old. Their age will increase to 4 on their next birthday.

In other cultures, age is counted differently. Some systems include the current year of life when stating a person’s age. So someone who is said to be 20 years old may actually be in their 21st year of life.

In one traditional Chinese age system, a baby is considered 1 year old at birth, and everyone’s age increases at the Lunar New Year—not on their birthday. So if a baby is born just one day before the Chinese New Year, they will be considered 2 years old just two days after birth.

Why Some Age Results May Seem Confusing

Sometimes, the way months and days are counted can be a little unclear—especially when the start date is at the end of a month. For instance, we typically count February 20 to March 20 as exactly one month.

But for a range like February 28, 2022 to March 31, 2022, there are two valid ways to interpret it:

• If you count February 28 to March 28 as one month, then the result is 1 month and 3 days.
• If you treat both February 28 and March 31 as end-of-month dates, then the result is 1 month.

Both methods are correct. Similar issues arise with dates like April 30 to May 31 or May 30 to June 30, due to the varying number of days in each month.

For this calculator, we use the first method: counting from date to date (e.g., Feb 28 to Mar 28) as one month.