In iOS, I need to know the actual time (UTC), not the time of the device. In other words, it should not be possible for the user to tamper with the time or date.
Anything that requires a network connection is not good (so accessing a time server is not an option).
AFAIK, there are 2 theoretical ways of achieving this:
- Use the timestamp from the GPS satellite signal
- Get the current time from the carrier
Problem is that this information is not exposed by any API in iOS.
Is there another way?
Most solutions you could possibly find (including getting GPS data from CoreLocation to access the time information) are flawed because they are depending on the actual device to access time time. You will need to connect to a time server (i would suggest to check for NTP server). I was looking at the core telephony framework and couldn't find anything that would provide the network time. You might want to fill a bug report and request apple to expand one of the classes to include the time.
You could have a look at secondsFromGMTForDate: and secondsFromGMT in NSTimeZone. If the GMT offset increases/decreases when the time of the device is changed, these provide a way to correct your timestamps to GMT (and probably convert to UTC).
You can't get to the raw GPS data and the timestamp property of the CLLocation in locationManager:didUpdateLocations: is set with the system clock
来源：https://stackoverflow.com/questions/12006245/is-there-a-way-to-determine-the-actual-time-and-date-in-ios-not-the-time-of-the