The User Login History plugin can track not only Login/Logout time of your website's visitors but also some more useful information that can definitely help you to know your website's visitors and hence increase your productivity.
Tracks the date and time of user's login, logout, last seen, etc.
Tracks user's login status to check if the user is logged in, logged out, failed, etc.
Tracks user's online status to check if the user is online, idle or offline.
Tracks user's old role, current role, username, etc.
Tracks user's operating system and browser.
Just install the plugin and start tracking.