From UTC Date String (ISO 8601).m

- (NSDate*)toISO8601Date{
  NSLocale* enUSPOSIXLocale = [[[NSLocale alloc] initWithLocaleIdentifier:@"en_US_POSIX"] autorelease];
  NSDateFormatter *dateFormatter = [[[NSDateFormatter alloc] init] autorelease];
  [dateFormatter setLocale:enUSPOSIXLocale];
  NSTimeZone *timeZone = [NSTimeZone timeZoneWithName:@"UTC"];
  [dateFormatter setTimeZone:timeZone];
  [dateFormatter setDateFormat:@"yyyy-MM-dd'T'HH:mm:ss.SSS'Z'"];
  NSDate* createdDate = [dateFormatter dateFromString:self];
  
  return createdDate;
}

To UTC Date String (ISO 8601).m

- (NSString*)toUTCDateString{
  NSLocale* enUSPOSIXLocale = [[[NSLocale alloc] initWithLocaleIdentifier:@"en_US_POSIX"] autorelease];
  
  NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
  [dateFormatter setLocale:enUSPOSIXLocale];
  NSTimeZone *timeZone = [NSTimeZone timeZoneWithName:@"UTC"];
  [dateFormatter setTimeZone:timeZone];
  [dateFormatter setDateFormat:@"yyyy'-'MM'-'dd'T'HH':'mm':'ss'.'SSS'Z'"];
  NSString *dateString = [dateFormatter stringFromDate:self];
  [dateFormatter release];
  return dateString;
}