类似朋友圈发布时间显示（刚刚... 多少分钟多少小时前 昨天）
- (NSString *)transformDateStrToMinutes:(NSString *)dateStr {

    NSDateFormatter *date=[[NSDateFormatter alloc] init];
    [date setDateFormat:@"yyyy-MM-dd HH:mm:ss"];
    NSDate *d=[date dateFromString:dateStr];
    NSTimeInterval late=[d timeIntervalSince1970]*1;

    //当前时间
    NSDate* dat = [NSDate dateWithTimeIntervalSinceNow:0];
    NSTimeInterval now=[dat timeIntervalSince1970]*1;

    //单位是秒
    NSTimeInterval cha=now-late;
    NSString *timeString= @"";
    if (cha / 3600 < 1) {
        //小时
        timeString = [NSString stringWithFormat:@"%f", cha/60];
        //        NSLog(@"timeString%@",timeString);
        timeString = [timeString substringToIndex:timeString.length-7];
        int num= [timeString intValue];
        if (num <= 1) {
             timeString = [NSString stringWithFormat:@"刚刚..."];
            //                NSLog(@"timeString = %@",timeString);
        }else{
            timeString = [NSString stringWithFormat:@"%@分钟前", timeString];
            //                NSLog(@"timeString = %@",timeString);
        }
     }
      //86400=1天
      if (cha / 3600 > 1 && cha / 86400 < 1){
          timeString = [NSString stringWithFormat:@"%f", cha/3600];
        timeString = [timeString substringToIndex:timeString.length-7];
        timeString=[NSString stringWithFormat:@"%@小时前", timeString];
        //            NSLog(@"timeString = %@",timeString);
      }
      if (cha/86400>1){
          timeString = [NSString stringWithFormat:@"%f", cha/86400];
        timeString = [timeString substringToIndex:timeString.length-7];
        int num=[timeString intValue];
        if (num<2){
            timeString = [NSString stringWithFormat:@"昨天"];
            //                NSLog(@"timeString = %@",timeString);
        }else {
              NSString * secondStr  = [dateStr substringFromIndex:5];
            timeString = [secondStr substringToIndex:11];
        }
      }
    return timeString;
}

时间戳转化为时间NSDate
- (NSString *)timeWithTimeIntervalString:(NSString )timeString
{
// 格式化时间
NSDateFormatter formatter =[[NSDateFormatter alloc] init];
formatter.timeZone = [NSTimeZone timeZoneWithName:@"beijing"];
[formatter setDateStyle:NSDateFormatterMediumStyle];
[formatter setTimeStyle:NSDateFormatterShortStyle];
[formatter setDateFormat:@"yyyy-MM-dd HH:mm:ss"];

    // 毫秒值转化为秒
    NSDate* date = [NSDate dateWithTimeIntervalSince1970:[timeString doubleValue]/ 1000.0];
    NSString* dateString = [formatter stringFromDate:date];
    return dateString;
}

将时间戳转化成具体时间字符串(具体到秒)
- (NSString *)transformTimeStampToTimeStr:(NSString *)timeStamp {
NSString *time = [NSString stringWithFormat:@"%f",[timeStamp doubleValue]];

    NSInteger num = [time integerValue]/1000;

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

    [formatter setDateStyle:NSDateFormatterMediumStyle];

    [formatter setTimeStyle:NSDateFormatterShortStyle];

    [formatter setDateFormat:@"YYYY-MM-dd HH:mm:ss"];

    NSDate * confromTimesp = [NSDate dateWithTimeIntervalSince1970:num];
    NSString * confromTimespStr = [formatter stringFromDate:confromTimesp];
    return confromTimespStr;
}