Wikipedia
Taskwarrior is an open-source, cross platform time and task management tool. It has a command-line interface rather than a graphical user interface.
Taskwarrior uses concepts and techniques described in Getting Things Done by David Allen, but is paradigm-agnostic in that it does not require users to adhere to any given life-management philosophy.
According to its author, Taskwarrior was created "to address layout and feature issues" in the Todo.txt applications popularized by Gina Trapani.
With Timewarrior the authors offer an accompanying tool to track time spent on projects. Configuration allows e. g. to define recurring breaks such as lunch time. The documention notes that "Timewarrior focusses on accurately recording time already spent, whereas Taskwarrior looks forward to work that is not yet done."