formatting and date validation

erpnext/www/book-appointment/1.html

@@ -12,7 +12,14 @@
     <div class="row justify-content-center mt-3">
         <div class="col-md-4 align-self-center ">
             <form name="myform">
-                <input type="date" name="appointment-date" id="appointment-date" class="form-control mt-3" min="{{ from_date }}" max="{{ to_date }}">
+                <input 
+                type="date" 
+                onchange="ondatechange()"
+                name="appointment-date" 
+                id="appointment-date" 
+                class="form-control mt-3" 
+                min="{{ from_date }}" 
+                max="{{ to_date }}">
                 <select name="appointment-timezone" id="appointment-timezone" class="form-control mt-3">
                     {% if timezones %}
                         {% for timezone in timezones%}