Display BIOS date correctly

include/PSX/Auxiliary/math_helper.hpp

@@ -1,7 +1,18 @@
 #pragma once
 #include "types.hpp"
+#include <stddef.h>
 
 namespace JabyEngine {
+    template<typename T>
+    static constexpr T pow(T base, T power) {
+        T result = base;
+        while(power > 1) {
+            result = result*base;
+            power--;
+        }
+        return result;
+    }
+
     template<typename T>
     static constexpr pair<T, T> div_and_mod(T value, T div) {
         const auto result = value/div;
@@ -12,4 +23,15 @@ namespace JabyEngine {
         const auto [tenth, rest] = div_and_mod(value, static_cast<uint8_t>(10));
         return (tenth << 4 | rest);
     }
+
+    template<typename T>
+    static constexpr T from_bcd(T value) {
+        T result = 0;
+
+        for(size_t n = 1; n < pow(10u, sizeof(T)*2); n *= 10) {
+            result += (value & 0b1111)*n;
+            value = value >> 4;
+        }
+        return result;
+    }
 }