aCalendar Tasks offers 

  • tasks management as separate module, which shows you your tasks as list (sorted A-Z, by due date or in manual sort mode with subtasks).
  • integration into the calendar views, so you can see your tasks on the due date and quickly create tasks for any date.
  • a dedicated Tasks widget
  • subtasks
  • timed tasks
  • recurring tasks
  • contact linking

As tasks backend we offer synchronisation with

  • Google Tasks
  • Open Tasks https://play.google.com/store/apps/details?id=org.dmfs.tasks (for local tasks and Caldav tasks)
  • Outlook / MS Exchange unfortunately Android offers no interface to tasks from Outlook or MS Exchange
  • Google Reminder / Google Keep unfortunately Google offers no interfaces to these services