Fix STEM ball date

Author: JoshuaWierenga

templates/header.html

@@ -33,6 +33,6 @@ <h1 class="me-auto">Programming Club</h1>
       </header>
       <div class="container">
         <div class="alert alert-info alert-dismissible fade show" role="alert">
-          <strong>STEM Ball 2025</strong> is on the 18th, see the <a href="https://campus.hellorubric.com/?eid=35210" class="alert-link">Rubric page</a> for more info
+          <strong>STEM Ball 2025</strong> is on the 20th of September, see the <a href="https://campus.hellorubric.com/?eid=35210" class="alert-link">Rubric page</a> for more info
           <button type="button" class="btn-close" data-bs-dismiss="alert" aria-label="Close"></button>
         </div>