Readdle made changes to their Calendars by Readdle app and renamed it to Calendars+. Then they released a brand new app with the original name, Calendars by Readdle, for free. Calendars by Readdle is a fully functioning app available for iPhone and iPad that allows you to manage your events while Calendars+ costs $6.99 and features additional options such as recurring events, multiple reminders, a task manager and the ability to invite people.