If you try to edit the Planned Start Date or Planned End Date of a parent task, the date you enter gets overwritten by the dates of the sub-tasks. f the parent task dates must be a calculation of the sub-task date, then it shouldn't even allow you to attempt to enter dates at the parent level. Or, if it does allow you to enter them, it should give you an error message.
The current way it works is confusing, because it lets you enter a date and then overwrites it. So if you just enter the date quickly without checking to see what it looks like after you save, you might be misled in believing your update was saved successfully.
