Detecting the First Game Login of the Day in Cocos Creator

Store the most recent login date locally, compare it with today, and update it when they differ:

const LAST_LOGIN_KEY = 'lastLoginDate';

function isFirstLoginToday(): boolean {
    const currentDate = new Date().toDateString();
    const lastLoginDate = cc.sys.localStorage.getItem(LAST_LOGIN_KEY);

    if (lastLoginDate !== currentDate) {
        cc.sys.localStorage.setItem(LAST_LOGIN_KEY, currentDate);
        return true;
    }
    return false;
}

if (isFirstLoginToday()) {
    console.log('First login today: grant the reward.');
} else {
    console.log('The player already logged in today.');
}

This is device-local state, so it can be reset by clearing storage and does not synchronize between devices. Use a trusted server date for authoritative rewards.