Web3 call should return different result based on time passed

Question

I am experiencing a weird issue. I am building a DApp where I want the new season of the game to start every 5 minutes (for testing purposes). However, web3 call returns old data, seems that it cached it and didn't refresh unless I send a tx. Here is a code snippet, smart contract:

uint public constant SEASON_DURATION = 5 minutes;

uint public start;

constructor() public {
    start = now;
}

function getCurrentSeason() public view returns (uint) {
    return (uint) ((now - start) / SEASON_DURATION);
}

React frontend:

const season = await myContract.methods.getCurrentSeason().call({from: activeAccount});

After 5 minutes pass, it still returns 0 even if I refresh the page. If I do a transaction (invoke any function in a smart contract), then getCurrentSeason() returns the correct value. What could be the solution?

I am using:

• web3 ^1.2.6
• Solidity v0.5.16
• Ganache (GUI version) v2.1.2
• Truffle v5.1.9
• Node v10.15.3
• Metamask wallet

Answer 1

Your problem is the fact that you're using a private network (emulated via Ganache), with no other miner participating. Therefore, now (aka block.timestamp) is never incremented.

Luckily for you, on Ganache you can emulate time via evm_increaseTime, for example:

web3.currentProvider.send({method: "evm_increaseTime", params: [300]});

See the official documentation for more details.