It can be possible in only B.C. i.e, Before Christ. That was about 2000 years ago.

Given,

In 1990 B.C = 2000 + 1990 = 3990 years ago, a person is 15 years Old

=> In 1995 B.C = 2000 + 1995 = 3995 years ago, the same person will be 10 years Old

Therefore, In 2000 B.C = 2000 + 2000 = 4000 years ago, the same person will be 5 years Old.