不要傻傻地以为 [NSDate date] 就是北京时间

NSDateFormatter *formatter = [[NSDateFormatter alloc]init];
NSTimeZone *timeZone = [NSTimeZone timeZoneForSecondsFromGMT:8*60*60]；
[formatter setTimeZone:timeZone];
[formatter setDateFormat:@"yyyy-MM-dd HH:mm:ss"];
NSDate *dateNow = [NSDate date];
NSString *beijingTimeStr = [formatter stringFromDate:dateNow];