How to handle timestamp in Solidity - ethereum

Question

I have written a smart contract which gets the block.timestamp and limits the caller to call the contract until the 2 hours passed as following:
mapping(address => uint256) public coffeKitchenLatestAqcuiredBalances;
function requestStarCoinFromCoffeeKitchenFaucet() public {
address callerAddress = msg.sender;
uint256 userLastRetrieveTime = coffeKitchenLatestAqcuiredBalances[callerAddress];
if (userLastRetrieveTime != 0){
uint256 epochNow = block.timestamp;
require(userLastRetrieveTime < epochNow - 7200,"You need to wait for 2 hours from your last call");
}
}
However I did not manage to extract to timestamp to limit the call time should be from 8AM to 6PM.
How can I format the epoch timestamp and check it on the smart contract call?

Answer 1

A great example of retrieving the hour from timestamp is in this library.
Since you might not want to import the whole library for just one function, here's a minimal implementation:
pragma solidity ^0.8;
library TimestampHelper {
uint constant SECONDS_PER_DAY = 24 * 60 * 60;
uint constant SECONDS_PER_HOUR = 60 * 60;
function getHour(uint timestamp) internal pure returns (uint hour) {
uint secs = timestamp % SECONDS_PER_DAY;
hour = secs / SECONDS_PER_HOUR;
}
}
contract MyContract {
function foo() external view {
uint currentHour = TimestampHelper.getHour(block.timestamp);
require(
currentHour >= 8 && currentHour <= 18,
"We're closed now. Opened from 8 AM to 6 PM UTC."
);
}
}