DoubleLinkedList

struct TElem
{
    struct TInfo
    {
        char name[30], surname[30], patr[30];
        int day, month, year;
    } info;
    TElem *next, *prev;
};

void deleteIncorrect(TElem *first)
{
    TElem *current = first;
    TElem *temp;
    while(current != nullptr)
    {
        if (1 > current->info.month || current->info.month > 12 || 1 > current->info.day || current->info.day > daysInMonthes[info.month-1])
        {
            current->prev->next = current->next;
            current->next->prev = current->prev;
            temp = current->prev;
            delete current;
            current = temp;
        }
        current = current->next;
    }

}