There is a lot of...problematic...advice here. For instance: Gary Woods <garygar...@earthlink.net> wrote on Thu, 16 Mar 2017 at 18:09:26 -0400 in <u53mcc534t4tu924pc6rpqklolf7oel...@4ax.com>:
> Not to gloat, but my Android phone is always spot on. I have a GPS > time app that shows the difference between GPS and phone time and > it's always in the tenths of a second area. Notice Gary doesn't specify which brand of Android phone, much less the specific model and carrier. This matters...a lot. For instance, my Verizon Samsung Galaxy S7 is regularly off by 300-700ms, and sometimes off by more than a second. A colleague's cell phone is regularly off by about 10 seconds. On the other hand, another colleague's Nexus {i forget what model} seems good to 10 ms. It's not clear to me how Android phones set their own time from the cell network, but I think the actual answer is "in many cases, not very well." The "ClockSync" android app will compare your phone's time to NTP, which does a pretty decent job. The "GPS Time" and other similar apps will compare your phone's time to UTC as derived from your phone's GPS receiver, although I think this is necessarily imprecise not only because of multipath but because of software issues between the GPS receiver and the phone. *handwave* I can't speak for iPhones, but for Android phones, it's really extremely hit-or-miss, and highly variable, both between models and even with a given phone from day to day. And if your threshold is something like half a second, you might think your phone is always good enough, and then have a rude awakening (I did!) when one day it's off by >1 second. --jh...@mit.edu John Hawkinson _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.