    function _participatePhase1() internal returns (uint256 oTAPTokenID) {
        uint256 _eligibleAmount = phase1Users[msg.sender];
        if (_eligibleAmount == 0) revert NotEligible();

        // Close eligibility
        phase1Users[msg.sender] = 0;

        // Mint aoTAP
        uint128 expiry = uint128(lastEpochUpdate + EPOCH_DURATION); // Set expiry to the end of the epoch
        oTAPTokenID = aoTAP.mint(msg.sender, expiry, uint128(PHASE_1_DISCOUNT), _eligibleAmount);
    }
...
    function exerciseOption(uint256 _aoTAPTokenID, ERC20 _paymentToken, uint256 _tapAmount)
        external
        whenNotPaused
        tapExists
    {
        // Load data
        (, AirdropTapOption memory aoTapOption) = aoTAP.attributes(_aoTAPTokenID);
        if (aoTapOption.expiry < block.timestamp) revert OptionExpired();
    function newEpoch() external tapExists {
        if (block.timestamp < lastEpochUpdate + EPOCH_DURATION) {
            revert TooSoon();
        }
...
    function exerciseOption(uint256 _aoTAPTokenID, ERC20 _paymentToken, uint256 _tapAmount)
        external
        whenNotPaused
        tapExists
    {
        // Load data
        (, AirdropTapOption memory aoTapOption) = aoTAP.attributes(_aoTAPTokenID);
        if (aoTapOption.expiry < block.timestamp) revert OptionExpired();
    function exerciseOption(uint256 _aoTAPTokenID, ERC20 _paymentToken, uint256 _tapAmount)
        external
        whenNotPaused
        tapExists
    {
        // Load data
        (, AirdropTapOption memory aoTapOption) = aoTAP.attributes(_aoTAPTokenID);
-       if (aoTapOption.expiry < block.timestamp) revert OptionExpired();
+       if (aoTapOption.expiry <= block.timestamp) revert OptionExpired();
