Does timestamp also change with nonce to calculate block hash in blockchain How hash is calculated

Question

Do we need to update the date timestamp on every hash calculation update? How it's implemented in the most popular cryptocurrencies?

function isValidHashDifficulty() { //validate calculated hash to fit requirements } function calculateHash(nextIndex, previousHash, timestamp, data, nonce) { //calculate hash } let nonce = 0; let nextIndex, previousHash, data; let timestamp = new Date().getTime(); // do we use this timestamp? while (!isValidHashDifficulty(nextHash)) { nonce = nonce + 1; timestamp = new Date().getTime(); //or do we get new date on every calculation attempt? nextHash = calculateHash(nextIndex, previousHash, timestamp, data, nonce); }

Answer 1

I was unable to locate the exact place in the Bitcoin codebase, but I am now certain that the timestamp does not change each time, since it would be a pretty meaningless operation that would just slow down the search for the solution to the mining puzzle. The timestamps of blocks in the blockchain are not required to be in the strictly increasing order. This is due to the fact that the network is distributed throughout the world, and there is no designated time zone that is to be used for timestamps.

Basically, a timestamp just needs to be "not too old", or if you want it more precisely: "a timestamp is accepted as valid if it is greater than the median timestamp of the previous 11 blocks, and less than the network-adjusted time + 2 hours"