关于日期和时间戳的转换比较

#pragma mark - 将某个时间戳转化成 时间
- (NSString *)getDateStringWithTimeStr:(NSString *)str{
    NSTimeInterval time=[str doubleValue]/1000;//传入的时间戳str如果是精确到毫秒的记得要/1000
    NSDate *detailDate=[NSDate dateWithTimeIntervalSince1970:time];
    NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init]; //实例化一个NSDateFormatter对象
    //设定时间格式,这里可以设置成自己需要的格式
    [dateFormatter setDateFormat:@"yyyy-MM-dd HH:mm:ss"];
    NSString *currentDateStr = [dateFormatter stringFromDate: detailDate];
    return currentDateStr;
}
#pragma  mark - 将字符串日期转换成想要格式的 NSDate

-(void)stringSwitchdate{
    
    NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
    
    [formatter setDateStyle:NSDateFormatterMediumStyle];
    
    [formatter setTimeStyle:NSDateFormatterShortStyle];
    
    [formatter setDateFormat:@"YYYY-MM-dd HH:mm:ss"];
    
    NSDate* date = [formatter dateFromString:[self timestampSwitchTime:1490354236 andFormatter:@"YYYY-MM-dd HH:mm:ss"]]; //------------将字符串按formatter转成nsdate
    
    NSLog(@"%@",date);
    
}



#pragma mark - 两个日期的时间差 返回秒数

-(void)differentTime{
    
    NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
    
    [formatter setDateStyle:NSDateFormatterMediumStyle];
    
    [formatter setTimeStyle:NSDateFormatterShortStyle];
    
    [formatter setDateFormat:@"YYYY-MM-dd HH:mm:ss"];
    
    NSDate *date1 = [formatter dateFromString:@"2017-03-24 19:42:30"];
    
    NSDate *date2 = [formatter dateFromString:@"2017-03-24 20:42:30"];
    
    //返回秒数
    
    NSTimeInterval aTimer = [date2 timeIntervalSinceDate:date1];
    
    
    
    int hour = (int)(aTimer/3600);
    
    int minute = (int)aTimer/60;
    
    NSString *dural = [NSString stringWithFormat:@"%d时%d分%f秒", hour, minute,aTimer];
    
    
    
    NSLog(@"%@",dural);
    
}

// 发布 1天转换成时间戳 距离1970多少秒
    NSDate *newDate = [nowDate dateByAddingTimeInterval:60 * 60 * 24 * ([_setDaysTextField.text floatValue])];
    long firstStamp = [newDate timeIntervalSince1970];
    // 时间戳转换成日期
    NSDate *confromTimesp = [NSDate dateWithTimeIntervalSince1970:firstStamp];
    NSLog(@"1296035591  = %@",confromTimesp);