To get the time in nano seconds or milli seconds use the following code snippet:
      mach_timebase_info_data_t sTimebaseInfo;
      uint64_t machTime = mach_absolute_time();
      // Convert to milliseconds
      mach_timebase_info(&sTimebaseInfo);
      machTime *= sTimebaseInfo.numer;
      machTime /= sTimebaseInfo.denom;
      machTime /= 1000000; // convert from nanoseconds to milliseconds
      return machTime;
For more on this look into the IOS docs: mach_absolute_time | Apple Developer Documentation
There is another method now, which we can use directly and make it more concise:
clock_gettime_nsec_np(CLOCK_UPTIME_RAW) 
For more details of the IOS version support check the chromium usage of this function:
There is another method:
double CurrentTime = CACurrentMediaTime();
But from the docs it looks like it will only return the time in seconds: CACurrentMediaTime() | Apple Developer Documentation
You will also use ‘NSDate’. But it will take the system time into consideration and if it syncs in between then time will jump: timeIntervalSince1970 | Apple Developer Documentation
Cheers and Peace out!!!