A regenerating task in Outlook is like a recurring task (one that shows up on a daily, weekly, or monthly basis) except that it recurs only when a certain amount of time passes after the last time you completed the task. Suppose you mow the lawn every two weeks. If it rains for a week, and one mowing happens a week later than usual, you still want to wait two weeks before the next one. To create such a regenerating task, follow these steps:

Open the task by double-clicking it.

The Task form appears.
Click the Recurrence button in the toolbar in the Task form (or press Ctrl + G).

The Task Recurrence dialog box opens.
Click Regenerate New Task.

Enter the number of weeks between regenerating each task.

Click OK.

A banner appears in the Task form describing the regeneration pattern.
Click Save and Close.

Your task appears in the list of tasks only once, but it has a different type of icon than nonrecurring tasks so that you can tell at a glance it's the regenerating type.
Remember, a regenerating task does not show up again until you mark the first instance completed. Also remember that a regenerating task does not make your grass grow -- it only reminds you that lawn mowing is never-ending.