etm provides a simple, intuitive format for using plain text files to store data, a command line interface for viewing events and tasks in a variety of convenient ways and a cross-platform, wx(python)-based GUI for creating and modifying events and tasks as well as viewing them. Displayed items can be grouped by year, month, day, week number, quarter, context, keyword, location, user, file and/or priority and can be filtered in comparable ways. The display shows the number of items and time totals broken down by group headings. A display of busy and free times is also supported. Alarms are supported for events and repetition for both events and tasks in a powerful and flexible manner.

QTodoTxt - Cross Platform todo.txt GUI