To be fair, I don't think they get much value from encrypted content. This doesn't mean they can't log every single thing you do with a timestamp attached to it. Privacy and anonymity are not the same thing.
Yes, they also get location (coarse or fine), media type (text chat, voice or video call), duration, any attachments sent (probably including file type, name and size, and frequency of contact, - all timestamped as you say.
Adding a bit to this the contents of the message are E2E encrypted but the metadata is probably still available (sender, receiver, timestamp, etc). FB probably already has the phone numbers of most of users in WhatsApp and can use the metadata to make inferred decisions about those users.
