Neptune orbits the sun every 164.8 years.....so that means that over the last 6,000 that Neptune has made its orbit only 36 times....That means if Neptune's age was to be measured in the same way we measure our age on this planet (a "year" for every time we orbit the sun) then by Neptune's standards it is only 36 years old...Interesting...
Hath in these last days spoken unto us by his Son,
whom he hath appointed heir of all things,
by whom also he made the worlds;
Hebrews 1:2