Block time calculation by block number in Polygon Mumbai Testnet

I definitely recommend invoking APIs, however, given your heavy requirement on NoAPIs, we'd have to go with estimates.

In this case -

• First, we need to find the average time per block. Polygon takes approximately - 2.5s to generate a new block - Data
• Then you'd need to identify the number of blocks that have already been generated (manual input in this case)
  • At the time of writing this answer - 36996889 blocks have been generated.
• Finally, you need the block number you want to get the time estimate for.
  • let's take 36996800 as an example in this case.

So, to identify the estimates (again, not accurate at all) you can use the following algorithm.

const currentBlockNumber = 36996889; const targetBlockNumber = 36996800; const averageTimePerBlock = 2.5;// Get the numenr of blocks that have been produced sinve the target block you're trying to estimate forconst numberOfBlocks = currentBlockNumber - targetBlockNumber;// Calculate the approximate time that the target block was produced atconst approximateTimeInSeconds = numberOfBlocks * averageTimePerBlock;// Calculate the approximate date and time that the target block was producedconst dateAndTimeCurrentBlockWasProducedAt = new Date(1671405095000); // This was the epoch currentBlock was produced atconst approximateTimeInMilliseconds = dateAndTimeCurrentBlockWasProducedAt.getTime() - (approximateTimeInSeconds * 1000); // get approx epoch for targetBlockconst approximateDate = new Date(approximateTimeInMilliseconds); // convert approxTime to human readable dateconsole.log(`The target block was produced approximately on ${approximateDate}.`);