To restore the "planned_date_begin" and "planned_date_end" fields to the task detailed view in Odoo, follow these steps:

1. Go to the Studio app and open the task view that you want to edit.

2. Click on the "Edit" button in the top right corner of the screen to enter edit mode.

3. On the left-hand side of the screen, click on the "Tabs" tab to view the available tabs.

4. Click on the tab where you want to add the "planned_date_begin" and "planned_date_end" fields.

5. Click on the "Add a field" button at the bottom of the tab.

6. In the search box that appears, type "planned_date_begin" and select the field from the list of suggestions.

7. Repeat the previous step for the "planned_date_end" field.

8. Click on the "Save" button in the top right corner of the screen to save your changes.

9. Click on the "Publish" button to make your changes live.

Now, you should see the "planned_date_begin" and "planned_date_end" fields in the tab view you selected.