Validate birthday in austrian insurance number

src/Rules/AustrianInsuranceNumber.php

@@ -38,6 +38,7 @@ public function isValid(mixed $value): bool
         return is_numeric($value)
             && $this->startsNotWithZero($value)
             && $this->hasValidLength($value)
+            && $this->hasValidBirthday($value)
             && $this->checkChecksum($value);
     }
 
@@ -51,6 +52,25 @@ private function startsNotWithZero(string $svnumber): bool
         return (int) $svnumber[0] !== 0;
     }
 
+    private function hasValidBirthday(string $svnumber): bool
+    {
+        $splittedBirthday = str_split(substr($svnumber, 4, 10), 2);
+
+        if (!in_array((int) $splittedBirthday[0], range(1, 31), true)) {
+            return false;
+        }
+
+        if (!in_array((int) $splittedBirthday[1], range(1, 20), true)) {
+            return false;
+        }
+
+        if (!in_array((int) $splittedBirthday[2], range(0, 99), true)) {
+            return false;
+        }
+
+        return true;
+    }
+
     private function checkChecksum(string $svnumber): bool
     {
         if (strlen($svnumber) !== $this->length) {

tests/Rules/AustrianInsuranceNumberTest.php

@@ -29,6 +29,10 @@ public static function dataProvider(): array
             [false, '8753080475'],
             [false, 'foo'],
             [true, '1230 011471'],
+            [false, '9999999999'],
+            [false, '9999202501'],
+            [false, '9999009901'],
+            [true, '1680250250'],
         ];
     }
 }