#sundowning

According to close Aides of Biden he is fine between 10am and 4 pm https://timesofindia.indiatimes.com/world/us/biden-operates-fine-between-10-4-debate-was-too-late-aides/articleshow/111382702.cms

To be fair to him and really see him at his best the next debate should likely take place at around 12 pm

On an unrelated note, dementia patients often succumb to what is called sundowning, where their brain just doesn't function very well at night. 

Maybe we can get a glimpse of him before the sundowning begins and we can actually make a decision on who to vote for that takes into account the best of each candidate.