Thanks Echo, you confirmed my guess (well at least partially). Any message sent to me (IM sent via email when I am offline), might go to a server in the UK, which is not in daylight saving time, and then that server puts the stamp, which in this case would be two hours behind for me. Now, I have only one doubt left. The person who sent the message lives in London and therefore the two hour behind could be explained as above. But what if a person lives in NYC? Would it still have the London, two hours behind timestamp, or would it have the a timestamp reflecting NYC time? In other words, the timestamp depends on the receiver or the sender ?
Sorry about all these questions, but I am intrigued by the technical "secrets" behind