What exactly does "time keeping abilities" mean? If I had to choose between 1) an NTP implementation with sub-millisecond accuracy that might allow a remote at

What exactly does "time keeping abilities" mean? If I had to choose between 1) an NTP implementation with sub-millisecond accuracy that might allow a remote attacker to execute arbitrary code on my server and 2) an NTP implementation which may be ~100ms off but isn't going to get me pwned, I'm inclined to pick option 2. Is writing an NTP server that maintains ~100ms accuracy not a solved problem?