Fix crash on IE 11 caused by passing date to Date constructor (#480)

Author: wojtekmaj

src/Calendar.jsx

@@ -25,6 +25,14 @@ const baseClassName = 'react-calendar';
 const allViews = ['century', 'decade', 'year', 'month'];
 const allValueTypes = [...allViews.slice(1), 'day'];
 
+function toDate(value) {
+  if (value instanceof Date) {
+    return value;
+  }
+
+  return new Date(value);
+}
+
 /**
  * Returns views array with disallowed values cut off.
  */
@@ -71,7 +79,7 @@ function getValue(value, index) {
     return null;
   }
 
-  const valueDate = new Date(rawValue);
+  const valueDate = toDate(rawValue);
 
   if (isNaN(valueDate.getTime())) {
     throw new Error(`Invalid date: ${value}`);