Dude, just use a timestamp.

no... time is relative! (no pun intended) - sending messages to the space station or a satellite in orbit would be off, or a moving,train, or a tall building... Did you know there are leap-seconds, just like there are leap-year? and atomic clocks are not yet standard on server/PC's, what is standard though is a time-client that will change the computers clock at some random intervals depending how much drift it has. A sequence number is also easier to parse.