Calendar: Fix hide/show of selected day contents

src/pretix/static/pretixpresale/scss/_calendar.scss

@@ -69,9 +69,6 @@
       background: darken($brand-primary, 15%);
     }
   }
-  .selected-day {
-    display: none;
-  }
 }
 .week-calendar {
   .weekday {
@@ -123,6 +120,13 @@
     }
   }
 }
+@media (min-width: $screen-sm-min) {
+  .table-calendar, .week-calendar {
+    .selected-day {
+      display: none !important;
+    }
+  }
+}
 @media (max-width: $screen-xs-max) {
   .table-calendar .day .events {
     display: none;