Immediatly when i create a post on my xenforo forum, the post is placed 2 hours later then i placed it according to the time stamp. (placing a post at 18:00 suddenly shows posted at 20:00) I checked with SSH on my server and the time is correct exept for a few minutes.
Assuming you have the correct time zone selected in XF, this is almost certainly down to the server time. The server has a time zone specified as well, so your time may not be correct given that time zone. (Also, if your time is off a few minutes, that's pretty significant; ideally you'll want to use something like NTP to maintain time synchronization.)