Comment 3 for bug 734622

Wolter> this feature is hard to design to be powerful enough and simple enough to use. There were some researches how other programs implement repeated tasks but nobody start to specify how it should be done.

There are many questions to solve, for example:
  * do we use existing system (ical) or we implement just subset of features
  * how to implement that? Should we just generate tasks on the behalf or we should implement a new type of task? What about infinite tasks (every monday do....)
  * when should a task be shown? If tasks repeats every day, I want to see tasks for the next/this week, but if the tasks repeats every week just once, I don't want to see all 7 instances. How to find the right time constant for that?
  * how to set repeating for a task?
  * ...

I created the very first version of specification (spec)/blueprint there: https://live.gnome.org/gtg/blueprints/repeated_tasks

You could help writing the spec, discussing about it. If you want to learn how to write such a spec, read Spolsky's howto: http://www.joelonsoftware.com/articles/fog0000000036.html