Todoist - Todoist is a to-do list that helps you get organized, at work and in life.
Google Calendar - Spend less time managing your day & more time enjoying it
Todo.txt - Track your tasks and projects in a plain text file, todo.txt. A todo.
Jorte - Schedule books must be practical and has a good design.
EssentialPIM - EssentialPIM is a free Personal Information Manager that keeps up with the times and lets you manage appointments, tasks, notes, contacts, password entries and email messages across multiple devices and cloud applications.
Business Calendar - Powerful and easy to use calendar app for Android including weather, widgets and tasks.