The way a person’s age is calculated can vary across different cultures. This calculator follows the most widely used age system, where age increases on a person’s birthday. For example, if someone has lived for 3 years and 11 months, their age is considered 3, and it will change to 4 on their next birthday. This method is common in most Western countries.

In other cultures, however, age may be counted differently. Some traditions include the current year in the calculation, which means that someone who is 20 years old may also be described as being in their 21st year of life. In the traditional Chinese system, a person is considered 1 year old at birth, and their age increases at the Chinese New Year instead of their birthday. So, if a baby is born one day before the New Year, they would already be considered 2 years old just two days later, even though they are only two days old.

Sometimes, calculating age in months and days can get tricky, especially when dates fall at the end of the month. For instance, the period from February 20 to March 20 is counted as one month. But if you calculate from February 28, 2022, to March 31, 2022, there are two valid interpretations: it could be one month and 3 days (if counting Feb. 28 to Mar. 28 as a month), or exactly one month (if considering both Feb. 28 and Mar. 31 as the end of their respective months). Both results are acceptable. Similar confusion arises with dates like April 30 to May 31 or May 30 to June 30, since months have uneven numbers of days. For consistency, this calculator uses the first method.