To edit the start or end time of a task’s time segment, select a desired task.
Then right click on a time segment in the Time Segment view located below the Task viewer. Click Modify Time on the menu that appears:
Pressing the Enter key while a time segment is selected will also bring up the Modify Time dialog in the same way the method of clicking on Modify Time will.
The third method for bringing up this dialog is available through the Time menu at the top of Grindstone.
Once the Modify Time Dialog appears for your desired time segment you will be able modify start dates, end dates, and add notes.