Whatsapp have has provided three category to hide Last Seen timestamp namely everyone,my contact and nobody. under the category of every one the information will be visible to all WhatsApp users.
If you select the option for my contact then the timestamp will be shown only to users added in your WhatsApp contact list while if you select5 the last option that is nobody then the information cannot be seen by any WhatsApp user and neither can you see their Last Seen information.
It should be noted that when you are Online then the information will be visible to all.
Here are the Steps to hide Last Seen timestamp on WhatsApp
click on Menu tab in whatsapp on the top right-corner and for those who have a menu button in the three capacitive button at the bottom can access it from there.
Under the Menu user will find Settings.
Tap on Settings and find Privacy option and select.
Under the Privacy, users can see the Last Seen option under Who Can See My Personal Info. Just tap on it and select whom do you want to show the information – Everyone , My contacts (Will not be visible to people other than WhatsApp contacts) and Nobody so that no one can see the info and neither can you see their Last Seen info.