IDBDatabase.onerror = function(event) { ... }

DBOpenRequest.onupgradeneeded = function(event) {
  var db = this.result;

  db.onerror = function(event) {
    note.innerHTML += '<li>Error opening database.</li>';
  };

  db.onabort = function(event) {
    note.innerHTML += '<li>Database opening aborted!</li>';
  };

  // Create an objectStore for this database

  var objectStore = db.createObjectStore("toDoList", { keyPath: "taskTitle" });

  // define what data items the objectStore will contain

  objectStore.createIndex("hours", "hours", { unique: false });
  objectStore.createIndex("minutes", "minutes", { unique: false });
  objectStore.createIndex("day", "day", { unique: false });
  objectStore.createIndex("month", "month", { unique: false });
  objectStore.createIndex("year", "year", { unique: false });

  objectStore.createIndex("notified", "notified", { unique: false });

  note.innerHTML += '<li>Object store created.</li>';
};