struct event {
  long seconds;
  char event_type; 
  };

event all_events[] = 
{
  {1, 'A'},
  {3, 'C'},
  {2, 'B'},
  {4, 'D'}
};

// used by qsort to sort an array
int cmpfunc (const void * a, const void * b) {
  return ( *(int*)a - *(int*)b );
}

void setup() { 
  Serial.begin(115200);

  for(int i=0; i < sizeof all_events / sizeof all_events[0]; i++)  
    Serial.println(all_events[i].event_type);

  // sort the other_events, so the hour events are in the correct spot
  size_t l = sizeof(all_events) / sizeof(all_events[0]);

  // qsort - last parameter is a function pointer to the sort function
  qsort(all_events, l, sizeof(all_events[0]), cmpfunc);

  for(int i=0; i < sizeof all_events / sizeof all_events[0]; i++)  
    Serial.println(all_events[i].event_type);
}

void loop() { 
  ;
}