How Do You Best Calculate Whole Years Gone By In Solidity?

Question

According to the Solidity docs, you cannot precisely calculate years based on the block.timestamp. I have an interest function compounding on an annual basis, so I only care when a whole year has gone by. If there are 2.99 years gone by since the contract was deployed, the interest calculation will consider that 2 years.

What is the best way to do this?

Here is what I have:

    uint public InitialBlockTime; /*Which is set in the contract constructor.*/

    function CalculateYearsGoneBy() public {
        YearsGoneBy = ((block.timestamp - InitialBlockTime)/31556926);
    }

31556926 is the average amount of seconds per year. Block timestamps are based on the Unix Epoch.

Answer 1

I think what you wrote seems fine. I might have written this instead:

(block.timestamp - InitialBlockTime) / 1 years;

But note that 1 years == 365 days, so it's not quite the same amount of time that you're using now. (I just find it easier to read/audit.)