将时间转化为距离当前时间的时间

+(NSString*)date:(NSString*)dateStr{

    

    NSCalendar *gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];

   

    NSUInteger unitFlags = NSHourCalendarUnit | NSMinuteCalendarUnit | NSSecondCalendarUnit | NSDayCalendarUnit | NSMonthCalendarUnit | NSYearCalendarUnit;

    NSDateFormatter *format=[[NSDateFormatter alloc] init];

    [format setDateFormat:@"yyyy-MM-dd HH:mm:ss"];

    NSDate *fromdate=[format dateFromString:dateStr];

    NSTimeZone *fromzone = [NSTimeZone systemTimeZone];

    NSInteger frominterval = [fromzone secondsFromGMTForDate: fromdate];

    NSDate *fromDate = [fromdate  dateByAddingTimeInterval: frominterval];

    NSLog(@"fromdate=%@",fromDate);

    NSDate *date = [NSDate date];

    NSTimeZone *zone = [NSTimeZone systemTimeZone];

    NSInteger interval = [zone secondsFromGMTForDate: date];

    NSDate *localeDate = [date  dateByAddingTimeInterval: interval];

    NSLog(@"enddate=%@",localeDate);

    NSDateComponents *components = [gregorian components:unitFlags fromDate:fromDate toDate:localeDate options:0];

    

    NSInteger second = [components second];

    NSInteger minute = [components minute];

    NSInteger hour = [components hour];

    NSInteger months = [components month];

    NSInteger days = [components day];//年[components year]

    NSLog(@"second=%d",second);

    NSLog(@"minute=%d",minute);

    NSLog(@"hour=%d",hour);

    NSLog(@"month=%d",months);

    NSLog(@"days=%d",days);

    

    NSString *srt;

    

    if (months==0&&days==0) {

        dateStr=[[dateStr substringFromIndex:11]substringToIndex:5];

        srt=[NSString stringWithFormat:@"今天 %@",dateStr];//今天 11:23

        srt=[NSString stringWithFormat:@"%d 分钟前发布",minute];//

    }else if(months==0&&days==1){

        dateStr=[[dateStr substringFromIndex:11]substringToIndex:5];

        srt=[NSString stringWithFormat:@"昨天 %@",dateStr];//昨天 11:23

        srt=[NSString stringWithFormat:@"%d 小时前发布",hour];//

    }else{

        dateStr=[dateStr substringToIndex:10];

        srt=dateStr;

    }

    return srt;

}