Timer.getFPGATimestamp() vs System.currentTimeMillis()

[fovea1959]

coming from a desktop/server Java background, I've always used System.currentTimeMillis() for elapsed time calcs, and we use it on our bot consistently.

Just noticed Timer.getFPGATimestamp(), which strikes me as *probably* being better than System.currentTimeMillis() (though the former might be using the latter for all I know).

Anyone have any insight as too whether the two differ significantly? Don't want to do the rework if not significantly better (though will start with Timer.getFPGATimestamp() next year!)