In Epicyon you can now schedule posts to be delivered at some time in the future. This can be useful for creating reminders to yourself to do things (eg. don't forget the milk) by posting a DM to yourself in the future. It could be used to promote an event by scheduling information posts leading up to it. Or it could also be used to handle time zone issues where you'd like a post to be seen but the expected recipients may not be awake if you post it right now.
With this type of feature there is the potential for spam, so the number of posts which can be scheduled at any point in time is quite small. Also spammers would have much easier methods for generating and sending a lot of posts, and the signature checking tends to mitigate against the kinds of spamming which happens with email.