better look for disabled days in themed calendar

src/common/DayTableMixin.js

@@ -375,9 +375,7 @@ var DayTableMixin = FC.DayTableMixin = {
 		var isDateValid = isDateWithinRange(date, view.activeRange); // TODO: called too frequently. cache somehow.
 		var classes = this.getDayClasses(date);
 
-		if (isDateValid) {
-			classes.unshift('fc-day', view.widgetContentClass);
-		}
+		classes.unshift('fc-day', view.widgetContentClass);
 
 		return '<td class="' + classes.join(' ') + '"' +
 			(isDateValid ?

src/common/common.css

@@ -68,11 +68,15 @@ body .fc { /* extra precedence to overcome jqui */
 	background: #d7d7d7;
 }
 
-.fc-disabled-day {
+.fc-unthemed .fc-disabled-day {
 	background: #d7d7d7;
 	opacity: .3;
 }
 
+.ui-widget .fc-disabled-day { /* themed */
+	background-image: none;
+}
+
 
 /* Icons (inline elements with styled text that mock arrow icons)
 --------------------------------------------------------------------------------------------------*/