You're correct, this is a bug. The programmer overlooked the issue of rolling over from one day (before midnight) to the next (after midnight). The likelihood that Chamberlain will quickly fix this problem is low. I suggest you contact customer service directly to report the issue. But in the meantime, you can work around this by setting 2 alerts, 1 from 10PM to 11:59 PM and 1 from 12 AM to 5:30 AM.