Person is 10 years old -Math riddle

In 1990, a person is 15 years old. In 1995, that same person is 10 years old. How can this be?


Explanation :  

The time must have been before Christ (BCE).

According to the Gregorian calendar, the Earth's timeline can be divided into two eras: Before Christ (BCE) and Anno Domini/Common Era (AD/CE).
In BCE, the years are reversed, so 1990 comes after 1995, and so on.
In the case of AD/CE, the years are listed in chronological order, so 1990 comes before 1995, and so on.

So, if someone was 15 years old in 1990, he or she would have been 10 years old in 1995, 5 years earlier.