Время прошедшее с определённой даты

int year,date,month,minutes,secondsres;
            time_t now;
            struct tm firstdate;
            double seconds;
 
            time(&now);  /* get current time; same as: now = time(NULL)  */
 
            firstdate = *localtime(&now);
 
            firstdate.tm_year= 103;
            firstdate.tm_hour = 22; firstdate.tm_min = 0; firstdate.tm_sec = 0;
            firstdate.tm_mon = 8;  firstdate.tm_mday = 25; 
 
            seconds = difftime(now,mktime(&firstdate));
            double year_temp,month_temp;
            year_temp=seconds/31556926;
            year=seconds/31556926;
            month_temp=(year_temp-year)*31536000/ 2592000;
            month=(year_temp-year)*31536000/ 2592000;
            date=(month_temp-month)*2592000/86400;

int dif, dmin, dhour, dday;
    
    time_t now,st1,st2;
    struct tm *tt1,*tt2;
    time (&now);
    tt1 = localtime(&now);
    tt2 = localtime(&now);
 
    tt1->tm_mon = this->GetMonth()-1;
    tt1->tm_mday = this->GetDay();
    tt1->tm_hour = this->GetHour();
    tt1->tm_min = this->GetMinute();
    st1 = mktime(tt1);  //got time1 in seconds
 
    tt2->tm_mon = t.GetMonth()-1;
    tt2->tm_mday = t.GetDay();
    tt2->tm_hour = t.GetHour();
    tt2->tm_min = t.GetMinute();
    st2 = mktime(tt2);  //got time2 in seconds
 
    dif = st1-st2;              //difference in seconds
    dif /= 60;                  //difference in minutes
    dmin = dif%60;              //minutes in difference
    dif /= 60;                  //difference in hours
    dhour = dif%24;             //hours in difference
    dif /= 24;                  //difference in days