How can I get the Correct Current Time in iOS?

Question

I know this it the repeated question. I have reviewed many answers but still didn’t get any solution.

My question is, How can I get the Time of Device if user have set it manually..?

I have implemented one chatting app. But in this app, I have issues of timings. If user have set manually time then how can we identify that.?

I want to get correct current UTC time. So using this, I can identify the difference between device time and UTC time.

If we are using, NSDate *currentDateAndTime = [NSDate date];, then it returns only UTC time according to device, not the current UTC time.

Is there any easy way to find out this solution?

Any help would be appreciated.

Solution 1

There is no trusted time source in iOS. You just operate with monotonic and non-monotonic time.

Monotonic time (or absolute time) represents the absolute elapsed wall-clock time since some arbitrary, fixed point in the past. The CACurrentMediaTime() or mach_absolute_time return monotonic time.

Non-monotonic time represents the machine's best-guess as to the current wall-clock, time-of-day time. It can jump forwards and backwards as the system time-of-day clock is changed. The [NSDate date] call returns it.

As an option, you can take the trusted date/time from the http Date response header. Then save it and current monotonic time(CACurrentMediaTime()) in the keychain. Here is the way to get the current trusted time:

last known online time + (CACurrentMediaTime() - saved monotonic time)

Another solution would be to use NTP server.

Solution 2

This might solve your problem

NSDate * date = [NSDate date];
        NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
        [dateFormatter setTimeZone:[NSTimeZone timeZoneWithAbbreviation:@"UTC"]];
        NSString *currentTime = [dateFormatter stringFromDate:date];
        NSLog(@"current time is:%@",currentTime);

Comments

[Meet Doshi]

It is not working, if you are setting manually time without using any time zone. It will returns on device time with UTC time.

[Nicolas Buquet]

Device always works using UTC time. Only the display of time use timeZone precision, but for display only.