Speed up PHP calculations

I wrote a simple program to count the number of Sunday days between two dates. If there are large gaps between dates, the script takes a very long time to execute. Can this be somehow optimized?

   $sunDay = 0;
   $start = DateTime::createFromFormat('m.d.X', "02.12.2023");
   $end = DateTime::createFromFormat('m.d.X', "04.12.292277026596");

   for ($i = $start; $i <= $end; $i = $i->modify('+1 day')) {
      if ($i->format('N') > 6) $sunDay++;
   }