This is one of the timeless games; it's always dark because this is Iceland in winter, but it's always day and the day never ends. You can even go to bed to make the tide change, but somehow no one else notices that 12 hours have passed.
Unlike normal walkthroughs, in Nice Game Hints you can select just the puzzle you want hints for. Here are listed the puzzles for "How does time work in this game?" in Nancy Drew: Sea of Darkness. The guide you choose only contains information about that puzzle, reducing possible spoilers for other puzzles.