New to Smart Contract development and am wondering if there is anyway to do a timed countdown inside a contract.

Basically I want to see if it's possible to trigger a process inside a contract that decrements or increments a value in the contract every x amount of seconds or minutes.

I wanted to see if this was possible to do internally? Or if the only way was to have some backend bot running to perform increment/decrement transactions.

Any insight is much appreciated! Thank You!

2 Answers 2


Rather than actually changing some variable over time, compute it on the fly.

E.g., to ask "How many seconds until x time?" you could write a function like this:

function secondsRemaining() public view returns (uint256) {
    if (x <= now) {
        return 0;  // already there
    } else {
        return x - now;

Essentially, a contract can't do anything by itself; it needs to be invoked via a transaction. But you can lazily compute the value instead when it's needed.


Every change on the Ethereum blockchain is always triggered from outside by a signed transaction. Hence, there is no way to implement a reoccurring timer within the smart contract itself. You'll always need to trigger it from outside.

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