well, Ideally, you wouldn't have separate files for each thing. You would have one "template" page that used the provided information (month=jan) to format the information from a database.
But, in your situation, since you already have the pages, you could simply use include statements to display the correct file, like so:
if ($month) {
$file_to_include="schedule-".$month.".php";
include ($file_to_include);
}