OP did you test your new script yet confirming it can detect to the milisecond when there's heavy flow of deposits ?
This is exactly what I want to know, thanks!
Ummmm, the protocol itself doesn't provide that kind of precision, at least the OP now has the timestamps agreeing with blockchain.info.
In short the best that can be done is within a second, anything more assumptions need to be made about received time however that is dependent upon the source of the TX and how it is broadcast to the network.