inspired by https://blog.oldj.net/2019/05/24/%E7%B4%A0%E6%95%B0%E6%97%A5/

find-prime-day.cpp

#include <iostream>
#include <cmath>
#include <string>
using namespace std;

bool isPrime(int num){
    if (num <= 1) return false;
    
    for(int i = 2; i <= sqrt(num); i++){
        if (num % i == 0) {
            return false;
        }
    }
    return true;
}

bool isPrimeDay(string date){
    int dateLength = date.length();
    
    for (int i = 0; i < dateLength; i++){
        if (!isPrime(stoi(date.substr(i, dateLength)))) {
            return false;
        }
    }
    return true;
}

void findPrimeDay(int yStart, int yEnd) {
  int date;
    for (int y = yStart; y <= yEnd; y++){
        for (int m = 1; m <= 12; m++){
            for (int d = 1; d <= 31; d++){
                if ( !(m == 1 or m == 3 or m == 5 or m == 7 or m == 8 or m == 10 or m == 12) and d == 31){
                    continue;
                }
                date = y * 10000 + m * 100 + d;
                
                if (isPrimeDay(std::to_string(date))) {
                    cout << date << endl;
                }
            }
        }
    }
}

int main(){
    findPrimeDay(1, 3000);
}