To insert a placeholder for a date and time in PowerPoint, follow these steps:

1. Open the PowerPoint presentation in which you need to add the date and time placeholder.
2. Click on the Insert tab in the ribbon.
3. Find and click on the Text dropdown button in the Text group.
4. Select Date & Time from the list of options.
5. Choose the appropriate Date format and Language from the respective dropdown menus provided.
6. Optionally, run the Update Automatically tickbox. This will ensure that the date and time placeholder is always up to date in the given language.
7. Click OK to insert the placeholder.