Allow a teacher or course admin to limit the dates (dates only, not times - from the beginning of start date to the ending of end date, both dates do not have to be set, start must come before or equal end date) between which posting is allowed in a given chatroom in a course. This would be controllable for each chatroom individually. The dates would be shown (if configured) so that all users (including the teacher) would know if/when students were allowed to post. The dates would control write access ONLY. Read access to the chatroom would be granted based on the permission only ("chat.read"). Write access would be granted in combination with the "chat.new" permission and the configured dates (empty or null dates would indicate that the chatroom is open and unrestricted by dates). Any user with "chat.revise.channel" will be able to change the date settings at any time.
This work would include adding date fields to the creation and editing screens, adding date storage columns to the database table(s), methods to store / retrieve the new date information, and updating and creating new methods to check the roles and date times for access.