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This age calculator operates on the most common international system, often called the “Western” system. In this method, a person’s age increases on the exact date of their birthday. For instance, an individual who has lived for 3 years and 11 months is considered to be 3 years old; their age will officially become 4 on their next birthday.

It is important to recognize that cultures count age differently. In some traditions, age is described by counting the number of years one has lived, where a person in their twenty-first year is said to be twenty years old. Another notable example is one traditional Chinese system, where a person is born at age 1. Furthermore, everyone’s age increases by one year on the date of the Traditional Chinese New Year, rather than on their personal birthday. This means a baby born just before the New Year would be considered 2 years old only days later.

Calculating the exact months and days between two dates can sometimes be confusing, particularly when dealing with the end of a month. This confusion arises from the uneven number of days in each month. For example, from February 28 to March 31, there are two valid interpretations: one could count one month and 3 days (from the 28th to the 28th) or simply one full month (treating both dates as the end of their respective months).

This calculator uses a specific method to resolve this ambiguity: it counts from a specific day in one month to the same day in the next month. Therefore, for a date range like February 28 to March 31, the result would be calculated as one month and 3 days. This same principle applies to other similar date transitions, such as April 30 to May 31.