Smart contract now vs javascript now

Question

I have a trouble with comparing timestamp parameter(in test) and now in smart contract.

Here is my smart contract:

function create(uint created_at) public {
    require(now > created_at, "The created_at should be less than now .");
}

And test function:

it("...should store the created_at", async () => {
    const storageInstance = await Storage.deployed();
    let created_at = new Date().getTime();//create utc now timestamp 
    await storageInstance.create(created_at);
 }

The test doesn't pass. Error:

The created_at should be less than now .

Answer 1

now in Solidity is the amount of seconds since the Epoch, (see Is the block.timestamp value in Solidity seconds or milliseconds?). Javascript's new Date().getTime() / Date.now() returns the amount of milliseconds since the Epoch (see Date.prototype.getTime & Date.now).

This means that Javascript's timestamp is always a factor 1000 larger than the one used by Solidity. You could change your JS code to divide the timestamp by 1000.

let created_at = Math.floor(Date.now() / 1000)

Also be mindful of goodvibration's comment in your design.

UPDATE: new Date().getTime() --> Date.now() (goodvibration's comment)