format current NSDate as ISO8601 string despite user's Calendar or 24-Hour-Format setting

gistfile1.m

- (NSString *)currentGregorianISO8601Date {
    NSDate *requestDate = [NSDate date];
    
    NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
    [dateFormatter setDateFormat:@"yyyy-MM-dd'T'HH:mm:ssZ"];
    
    // WORKAROUND http://openradar.appspot.com/radar?id=1110403
    [dateFormatter setLocale:[[NSLocale alloc] initWithLocaleIdentifier:@"US"]];
    
    // translate to Gregorian calendar if other calendar is selected
    NSCalendar * gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
    [gregorian setTimeZone:[NSTimeZone timeZoneWithAbbreviation:@"GMT"]];
    [dateFormatter setCalendar:gregorian];

    NSString *dateString = [dateFormatter stringFromDate:requestDate];
    NSLog(@"%@",dateString);
    return dateString;
}