We know, that our cells replace themselves on a regular basis. Seems only logical that at one point, they’ll all be replaced at least once. So we’re a new person at 7 years old, 14, 21, …
But wait, do we start counting at birth? Or at conception? From the moment a specific organ is formed? All organs are formed? When do the seven years begin?

I think, its might not be logical too... There's no time we can start counting... Because as new cells are forming, others are dying...