Due is another app specifically designed for iPhones and iPads that allows you to jot down tasks and set reminders quickly. Using an exclusive app to track tasks is a good way to de-clutter your calendar. It is extremely easy to modify reminders with Due. If there is a change of plans, you can reschedule your plan by editing the reminder on the fly. This one-tap option to manage events makes it a simple app for managing events. The app also provides persistent reminders with auto snooze options. Until you mark the task as complete or reschedule the task, the auto snooze repeatedly notifies you of a task. You are also able to send reminders to friends and co-workers.