alt Hacker NewsI was doing something at work that involved calculating round trip times from/to Android devices, and learned that although it should be possible for NTP to sync clocks with below-second precision, in practice many of the Android devices I was working with (mostly Pixels 2-7) were off from my server and each other by up to 5 seconds, which blew my mind.
Replies
Nextgrid • today at 2:04 PM
Depending on carrier-specific configuration and firmware phones may be configured to prefer NITZ (time transmitted by the cellular network) instead of NTP. That time is probably what’s off and would explain your observation.
winrid • today at 3:52 AM
Yeah it can only do so much with varying latency
It's hard to keep a phone's clock closely synchronized because they experience a lot of temperature swings, going between pockets and hands and open air and sometimes in direct sun, and the processor goes between idle and 100% as well.
Once you get to internationa phones, you'll have places where the phone does not include all timezones and specifically is missing the actual local timezone, so automatic sync is typically disabled so that the time can be set so that the displayed time matches local time... even if that means the system time is not correct.