1. Launch Whatsapp on your phone
2. Go to Whatsapp Settings
3. In Whatsapp settings, head over to ‘Privacy Settings‘
4. In Privacy Settings, you have the option for ‘Last Seen‘
5. By default, this option will be set to Everyone. You can change it to show your last seen status to ‘My Contacts‘ or for none.
6. Select ‘Nobody‘ for the Last Seen option.
7. Now, nobody will be able to see when you were last seen on Whatsapp.
Note that if you set ‘Last seen‘ on Whatsapp to ‘Nobody‘, you will also not be able to see other user’s last seen. It is a two way thing.