timestamp. message sent or message recieved

Does anyone know if the timestamp above a facebook messenger message that I've recieved is the time it was sent or the time it was recieved on my phone. I suppose this applies to facebook on a pc/mac too. And if I tried to send a message but I had no internet connection...would the message wait until I had a connection....and then the recipient see the time I had actually written it and pressed send....