计算 距离现在的时间

//计算 距离现在的时间

-(NSString *)getUTCFormateDate:(NSDate *)newsDate {
    NSString *dateContent;
    NSTimeInterval secondsPerDay = 24 * 60 * 60;
    NSDate *today=[[NSDate alloc] init];
    NSDate *yearsterDay =  [[NSDate alloc] initWithTimeIntervalSinceNow:-secondsPerDay];
    NSDate *qianToday =  [[NSDate alloc] initWithTimeIntervalSinceNow:-2*secondsPerDay];
    //假设这是你要比较的date：NSDate *yourDate = ……
    //日历
    NSCalendar* calendar = [NSCalendar currentCalendar];
    unsigned unitFlags = NSYearCalendarUnit | NSMonthCalendarUnit |  NSDayCalendarUnit;
    NSDateComponents* comp1 = [calendar components:unitFlags fromDate:newsDate];
    NSDateComponents* comp2 = [calendar components:unitFlags fromDate:yearsterDay];
    NSDateComponents* comp3 = [calendar components:unitFlags fromDate:qianToday];
    NSDateComponents* comp4 = [calendar components:unitFlags fromDate:today];
    if ( comp1.year == comp2.year && comp1.month == comp2.month && comp1.day == comp2.day) {
        dateContent = @"昨天";
    }
    else if (comp1.year == comp3.year && comp1.month == comp3.month && comp1.day == comp3.day) {
        dateContent = @"前天";
    } else if (comp1.year == comp4.year && comp1.month == comp4.month && comp1.day == comp4.day)
    {
        dateContent = @"今天";
    }
    else {
//返回0说明该日期不是今天、昨天、前天
        dateContent = @"0";
    }
    return dateContent;
}