Animal Crossing New Horizons’ gameplay is based on real time and affects Nook’s Cranny store hours. Some key features are tied to the in game time. If you are interested in max bells, you need to visit Nook’s Cranny and sell a stack of turnips during store open hours, 8AM to 10PM between Monday and Saturday. On Sunday, Timmy and Tommy don’t buy turnips. Since I have ACNH six treasure islands, I’ve offset the time and dates so there should be at least one island open with max bells (Hocus Pocus, Star Hallow, Pangea, or Supernova), and one with standard high priced turnips (606 turnip price on Cat Land and Pile of Cats). Here is the live time on all of the islands:
Nook’s Cranny store hours are affected by in game time. Get your max bells or 606 turnip price while Nook’s Cranny is open on Pange’s treasure islands!

Just a note, that your own game time does not affect the treasure island game time. So if you fly into an island and Nook’s Cranny is not open, changing your personal game time by time travelling on your Switch system settings will have no affect on Nook’s Cranny opening hours on my treasure islands. Take a look at the lists above and see what island works for the store hours.
If you fly into an island where the store should be open but it instead displays “the store is closed due to circumstances.” the island dodo code is from the previous day and needs to be reset to reopen. Visit the #island-help area on Discord to request a new dodo to be created.
If you’re not a member of my treasure islands yet, check out my treasure island info page for details on how you can access my islands!