It's a good question. However, I would like to hope that for an entirely virtual conference such as this it would be decided to schedule talks at all hours. This reduces the chance of speakers, wherever they may be, from having to present in the middle of their night. Further, since every presentation will already be digital there's less extra work involved in making them all available as recordings after the fact so that "attendees" should easily be able to view all talks shortly after they finish.

If talks are spread around the clock that means less concurrency as well so your chances of being able to attend all the talks of most interest to you as they happen increase greatly.