Use UTC dates to make the polypill consistent with native inputs

src/input.js

@@ -38,7 +38,7 @@ export default class Input {
             return new Date(parts[fmt.yyyy], parts[fmt.mm] - 1, parts[fmt.dd])
           },
           set: val => {
-            this.element.value = dateFormat(val, this.format)
+            this.element.value = dateFormat(val, this.format, true)
           }
         },
         valueAsNumber: {