without Windows OS

# define timeradd(a, b, result)
  do {                                        
    (result)->tv_sec = (a)->tv_sec + (b)->tv_sec;                 
    (result)->tv_usec = (a)->tv_usec + (b)->tv_usec;                  
    if ((result)->tv_usec >= 1000000)                         
      {                                       
    ++(result)->tv_sec;                           
    (result)->tv_usec -= 1000000;                         
      }                                       
  } while (0)

# define timersub(a, b, result)                           
  do {                                        
    (result)->tv_sec = (a)->tv_sec - (b)->tv_sec;                 
    (result)->tv_usec = (a)->tv_usec - (b)->tv_usec;                  
    if ((result)->tv_usec < 0) {                          
      --(result)->tv_sec;                             
      (result)->tv_usec += 1000000;                       
    }                                         
  } while (0)