WhatsAPI how to manually send my lastseen to the whatsapp server may be to a previous date?
I'm Using whats app api from https://github.com/shirioko/WhatsAPINet
You can't any more. That loophole has been fixed in the underlying API for years. Now you can only indicate to WhatsApp who should be able to see your LastSeen timestamp, but the calculation of the actual timestamp value to be displayed is handled entirely server-side.