To set a Hidden until date:
Access the course gradebook via the grades link in the course administration block.
Select Categories and items from the gradebook drop-down menu.
Click on the edit icon opposite the activity for which a Hidden until date is to be set.
On the edit grade item page, ensure that advanced settings are displayed. (Click the Show advanced button if not).
Enable the Hidden until setting by unchecking the disable checkbox, then set a date.
Click the Save changes button.