Objective-C, How can I get the current date in UTC

Question

I am trying:

NSDate *currentDateInLocal = [NSDate date];
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:@"yyyy-MM-dd'T'HH:mm:SS.SSS'Z'"];
NSString *currentLocalDateAsStr = [dateFormatter stringFromDate:currentDateInLocal];

NSDateFormatter * dateFormatter2 = [[NSDateFormatter alloc] init];
NSTimeZone *timeZone = [NSTimeZone timeZoneWithName:@"UTC"];
[dateFormatter2 setTimeZone:timeZone];
[dateFormatter2 setDateFormat:@"yyyy-MM-dd'T'HH:mm:SS.SSS'Z'"];
NSDate *currentDateInUTC = [dateFormatter2 dateFromString:currentLocalDateAsStr];

but It's still does not represent the current UTC time, how can I achieve this?

Thanks

Answer 1

Still another way to do it is like so in a C++ class in your Objective C project. (So, make a .mm file and build a C++ class with public and private parts, and stick this in the public part (unless you need it private).) Then, reference it like NSString *sNowUTC = MyClass::getUTCTimestamp();.

static NSString *getUTCTimestamp(){
  time_t rawtime;
  struct tm * timeinfo;
  char buffer [80];
  time (&rawtime);
  timeinfo = gmtime (&rawtime);
  // make format like "2016-06-16 02:37:00" for 
  //   June 16, 2016 @ 02:37:00 UTC time
  strftime (buffer,80,"%F %T",timeinfo);
  std::string sTime(buffer);
  NSString *sUTC = @(sTime.c_str());
  return sUTC;
}

Answer 2

NSDate *currentDate = [[NSDate alloc] init];

Now it is in UTC, (at least after using the method below)
To store this time as UTC (since refernce date 1970) use

double secsUtc1970 = [[NSDate date]timeIntervalSince1970];

Set Date formatter to output local time:

NSTimeZone *timeZone = [NSTimeZone defaultTimeZone];
// or Timezone with specific name like
// [NSTimeZone timeZoneWithName:@"Europe/Riga"] (see link below)
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setTimeZone:timeZone];
[dateFormatter setDateFormat:@"yyyy-MM-dd'T'HH:mm:ss.SSS'Z'"];
NSString *localDateString = [dateFormatter stringFromDate:currentDate];

Available NSTimeZone names

A NSDate object always uses UTC as time reference, but the string representation of a date is not neccessarily based on UTC timezone.

Please note that UTC is not (only) a timeZone, It is a system how time on earth is measured, how it is coordinated (The C in UTC stands for coordinated).
The NSDate is related to a reference Date of midnight 1.1.1970 UTC, altough slightly wrongly described by Apple as 1.1.1970 GMT.

In the original question the last word timeZone is not perfect.