Question

In 1990 a person is 15 years old. in 1995 the same person is 10 years old. how is this possible?

Answer 1

It is possible if it is 1990 BC and 1995 BC.
Then the person who is 10 years old in 1995 BC after 5 years ( in 1990 BC ) is 15 years old:
1995 BC  + 5 years = 1990 BC
10 years + 5 years = 15 years