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contracts...EventsContract.sol

// SPDX-License-Identifier: GPL-3.0
pragma solidity >=0.7.0 <0.9.0;

contract EventsContract {
    // Represents the time when the bidding will end
    uint biddingEnds = block.timestamp + 5 days;

    struct HighestBidder {
        address bidder;
        string bidderName;
        uint bid;
    }

    // Variable of type HighestBidder
    HighestBidder public highestBidder;

    // Events emitted by contract
    // Whenever a high bid is received
    event NewHighBid(address indexed who, string name, uint howmuch);

    // High bid preceded by this event
    event BidFailed(address indexed who, string name, uint howmuch);

    // Ensures that bid can be received i.e, auction not ended
    modifier timed {
        if(block.timestamp < biddingEnds){
            _;
        } else {
            /**throw an exception */
            revert("Throw an exception");
        }
    }

    constructor()  {
        // Starts the bidding at 1 ether
        highestBidder.bid = 1 ether;
    }

    
    // Payable since ether should be coming along
    // Timed, we need to end this bidding in 5 days
    function bid(string memory bidderName) public payable timed {
        if(msg.value > highestBidder.bid) {
            highestBidder.bidder = msg.sender;
            highestBidder.bidderName = bidderName;
            highestBidder.bid = msg.value;
            // Received a high bid - emit event
            emit NewHighBid(msg.sender, bidderName, msg.value);
        } else {
            // Received bid less than high bid emit event
            emit BidFailed(msg.sender, bidderName, msg.value);
            // throwing exception would return the ethers
            revert("Throw an exception");
        }
    }
}

This is an example of using modifiers/events and time in a contract. The struct is a common data structure used in solidity in this example using it to create the highestBidder object.

Notes about events

• Part of the contract ABI
• Must subscribe to the event in frontend/web application
• Runs on all nodes