Is it (really) possible to sync time across multiple (not inter-connected) iOS devices to within a few milliseconds accuracy? The only possible solution I (and others, according to Stack Overflow) can think of is sync the devices with a time server(s) over NTP.
Multiple sources state:
NTP is intended to synchronize all participating computers to within a few milliseconds of Coordinated Universal Time (UTC). It uses the intersection algorithm, a modified version of Marzullo's algorithm, to select accurate time servers and is designed to mitigate the effects of variable network latency. NTP can usually maintain time to within tens of milliseconds over the public Internet, and can achieve better than one millisecond accuracy in local area networks under ideal conditions. Asymmetric routes and network congestion can cause errors of 100 ms or more.
Can NTP really achieve accuracy within the few milliseconds level?