Third.
Improved reset/align code, and resetting when the lag exceeds 20 ms. The raw NTP is being filtered by cascading outlier filters before averaging to get the correction. Looking at the NTP polls, it amazing how fast system time is 20 ms off of UTC. Or in the prior chart, 250 ms off of UTC.
So if one is using system time to create timestamps, if your load is nice and steady, then they might be close. But if the actual time of the timestamp matters, rather than just the order, you may wish to take a closer look between the time you're using to timestamp from vs. UTC.
When I compared the time adjustments I saw in the IB logs, there were very very close to the NTP UTC.
