The forum cron checks posts to be sent to users, and only checks for posts created in the last two days - ostensibly to protect users from a flood of emails if the cron hasn't been running for several days. However, if a discussion has been marked as 'Hidden until ...' the cron is checking the post created date first, and then checking if the discussion is currently hidden. This means that posts created more than two days previous will never be notified to the student, regardless of the 'Hidden until' date.

This change checks if the post has been created in the last two days OR if the display date occurred within the last two days, then processes it as normal (digest or immediate mailout).