Obviously the date changes at midnight, but my house and mayor/construction permit status haven't changed. Pretty sure waiting "1 day" used to mean on the next date (I skipped CF)? So when does the town update?
If it's 6 AM and you are still playing, Isabelle will make an announcement from the town hall stating that it is 6 AM and time for everyone to wake up. Then, the game will save automatically and you'll walk out of your house when it's finished. Happened to me today
^ Yep happened to me this morning while I was playing too... not that I... err... set my alarm for 5 A.M. so I could play Animal Crossing before work or anything.
Yeah, 6am is when it is considered the 'next day'. So if you have any kind of project in the works like a house expansion or a public works project, 6am is when any changes go forward.