As an example...you leave the hotel lot to visit another community lot at 9am, you stay at the community lot until 6pm, at 12 noon while your visiting the community lot, the game will register that your staying another day at the hotel (you get no message about this though), when you return to the hotel, the time is back to 9am when you left and you also get a message saying you missed checkout time and 1 day has been added to your hotel charge.
Time passes in my game! When I leave the hotel at 9 am and come back at 6 pm, it is 6 pm in the hotel. It does not matter, if I visit the community lot with my whole family or with just one of them...