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.

CalendarZ - CalendarZ is a simple yet high-level calendar application, introduced lots of advanced functions and features.

Task Coach - Task Coach is a simple open source todo manager to keep track of personal tasks and todo lists.

CalenGoo - Features | 1.0.175 for Android™

Strikethru - Strikethru is a kind of to-do list notebook for managing work lists and staying updated with the important tasks.