When in the day do CourseBot messages actually go out?

Course units go out at the start of a day, just after midnight Western Australian time (8 hours ahead of GMT; 9 in summer). So if you've got a course unit scheduled for, say, tomorrow, it will go out tonight when the clock ticks over.

This is important if you're scheduling a unit to go out "later tonight". Don't schedule it for today's date, because that will already have passed. Schedule it for tomorrow.

Note: If you've got a unit scheduled for "0 days" (i.e. a welcome message), none of this applies. The unit goes out immediately when somebody subscribes to the course.