As with the basic calendar kindle fire hd: Can not create an appointment a half hour on a recurring basis. A first sync with your other devices, appointments with half hours are automatically reduced to one hour. For specific events, no problem. But for the appointment of repetitions on each week, at the slightest sync calendars are not harmonized within this manually or prevent synchronizations kindle the fire. This limits the usefulness of the use of the calendar. It's a shame because the application seems intuitive and convenient. Luckily I got it for free ...