disable now button if its range is invalid

src/Calendar.js

@@ -970,7 +970,10 @@ function Calendar_constructor(element, overrides) {
 	t.updateToolbarButtons = function() {
 		var now = t.getNow();
 
-		if (isDateWithinRange(now, currentView.currentRange)) {
+		if (
+			isDateWithinRange(now, currentView.currentRange) ||
+			!currentView.computeDateIsValid(now)
+		) {
 			toolbarsManager.proxyCall('disableButton', 'today');
 		}
 		else {

src/common/View.js

@@ -365,6 +365,11 @@ var View = FC.View = Class.extend(EmitterMixin, ListenerMixin, {
 	},
 
 
+	computeDateIsValid: function(date) {
+		return this.resolveRangesForDate(date).isValid;
+	},
+
+
 	trimHiddenDays: function(inputRange) {
 		return {
 			start: this.skipHiddenDays(inputRange.start),