Dim out past days in calendar

public/css/style.css

@@ -1262,6 +1262,9 @@ span.select2-container.select2-container--default.select2-container--open {
 .fc .fc-highlight {
     background: rgba(188, 232, 241, 0.6) !important;
 }
+.fc .fc-day-past {
+    background: #e7e7e7 !important;
+}
 .fc .add-overlay {
     padding: 1px 4px;
     display: inline-block;