The new update of WhatsApp to hide information that shows whether the user is "online" when was the "last seen online".
Nothing is new feature is only available to iPhone users. This lets you keep your privacy by not informing the other contact when we are connected or not.
To disable this message showing a very useful information, go into the settings, application settings and chat in the Advanced section, clear the "Last time online" function.
From the company notified that their total deactivation may be prolonged up to 24 hours. Also expected to be available soon on Android, BlackBerry and Symbian.