If your business is open 24 hours for certain days, start at 12:00 AM and end at 11:59 PM. Then go to the view tab and check the "display 24 hours" option:

Step 1: Make sure you start at 12:00 AM and end at 11:59 PM

Step 2: Select Display open 24 hours for certain days

Now when you visit the widget, you can see that instead of opening hours, it shows "open 24 hours":