How to identify Who holds an NFT for how long?

Question

I am developing an NFT collection using ERC721 token. But I would like to know how a particular nft is held by a particular customer?

I am sensing there are two selling option one is minting fropm my website another one is buying from opensea?

Is that any way I can do that?

Answer 1

The ERC-721 contract uses this mapping(uint256 => address) private _owners; to store the owner. If you want to keep track of how long an address has holded a particular NFT you can create a struct

struct Owner {
  address ownerAddress;
  uint256 sinceWhen;
}

You then need to modify some functions (like mint, transfer, ...) and you set the sinceWhen as the block.timestamp.