Think mobile devices. The user often doesn't know what is correct (eg how many Americans would know about Arizona) and there is a fair amount of data behind th

Think mobile devices. The user often doesn't know what is correct (eg how many Americans would know about Arizona) and there is a fair amount of data behind the calculations of where you actually are. On a laptop with good net connections you could download that database. Other devices are more constrained. I have an Android tablet that is wifi only and hence cannot get time details from cell towers. I use this app which corrects the time via NTP, and updates the timezone information automatically by querying geonames. https://market.android.com/details?id=ru.org.amip.ClockSync https://market.android.com/details?id=ru.org.amip.ClockSync