• 参照 http://www.jianshu.com/p/ffc758b8eb0e 并对其做了更新

• [需求] 如果当前系统时间和北京时间相差大于1小时则提示用户去设置时间

• 使用最新NSURLSession

• 在application: didFinishLaunchingWithOptions:中调用

• 注意 弹框需要切回主线程,否则程序会卡在启动页

- (void)checkSystemTimeInterval{
    NSString *urlString = @"https://m.baidu.com";
    urlString = [urlString stringByAddingPercentEncodingWithAllowedCharacters:[NSCharacterSet URLQueryAllowedCharacterSet]];
    NSMutableURLRequest *request = [[NSMutableURLRequest alloc] init];
    [request setURL:[NSURL URLWithString: urlString]];
    [request setCachePolicy:NSURLRequestReloadIgnoringCacheData];
    [request setTimeoutInterval: 60];
    [request setHTTPShouldHandleCookies:FALSE];
    [request setHTTPMethod:@"GET"];
    
    NSURLSession *session = [NSURLSession sharedSession];
    NSURLSessionDataTask *dataTask = [session dataTaskWithRequest:request completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) {
        NSHTTPURLResponse *httpResponse=(NSHTTPURLResponse *)response;
        if ([response respondsToSelector:@selector(allHeaderFields)]) {
            NSDictionary *dic=[httpResponse allHeaderFields];
            //NSLog(@"dic:%@",dic);
            NSString *date = [dic objectForKey:@"Date"];
            date = [date substringFromIndex:5];
            date = [date substringToIndex:[date length]-4];
            NSDateFormatter *dMatter = [[NSDateFormatter alloc] init];
            dMatter.locale = [[NSLocale alloc] initWithLocaleIdentifier:@"en_US"];
            [dMatter setDateFormat:@"dd MMM yyyy HH:mm:ss"];
            NSDate *netDate = [[dMatter dateFromString:date] dateByAddingTimeInterval:60*60*8];
            
            NSTimeZone *zone = [NSTimeZone systemTimeZone];
            NSInteger interval = [zone secondsFromGMTForDate: netDate];
            NSDate *netLocalDate = [netDate  dateByAddingTimeInterval:interval];
            NSLog(@"netLocalDate=%@",netLocalDate);
            
            NSDate *localDate = [NSDate mylocalDate];
            int timeout =  [localDate timeIntervalSinceDate:netLocalDate];
            NSLog(@"timeout=%zd,localDate=%@,netDate=%@",timeout,localDate,netLocalDate);
            
            if (abs(timeout)>60*60) {
                dispatch_async(dispatch_get_main_queue(), ^{
                    UIViewController *currentVc = [(UINavigationController *)[[UIApplication sharedApplication].windows firstObject].rootViewController visibleViewController];
                    UIView *currentView = currentVc.view;
                    //获取到当前显示View,可弹框提示
                    dispatch_async(dispatch_get_main_queue(), ^{  
                        //对UI操作要切回主线程
                    });
                });
            }
        }
    }];
    [dataTask resume];
}

• 附

• 跳转去设置系统时间的code(iOS8.0+)

[[UIApplication sharedApplication] openURL:[NSURL URLWithString:@"prefs:root=General&path=DATE_AND_TIME"]];

• NSDate扩展

+ (NSDate *)mylocalDate
{
    NSDate *date = [NSDate date];
    
    NSTimeZone *zone = [NSTimeZone systemTimeZone];
    
    NSInteger interval = [zone secondsFromGMTForDate: date];
    
    NSDate *localeDate = [date  dateByAddingTimeInterval: interval];
    
    return localeDate;
}