Datetime date initial value fix (#6483)

esphome/components/web_server/web_server.cpp

@@ -914,7 +914,7 @@ void WebServer::handle_date_request(AsyncWebServerRequest *request, const UrlMat
 std::string WebServer::date_json(datetime::DateEntity *obj, JsonDetail start_config) {
   return json::build_json([obj, start_config](JsonObject root) {
     set_json_id(root, obj, "date-" + obj->get_object_id(), start_config);
-    std::string value = str_sprintf("%d-%d-%d", obj->year, obj->month, obj->day);
+    std::string value = str_sprintf("%d-%02d-%02d", obj->year, obj->month, obj->day);
     root["value"] = value;
     root["state"] = value;
   });