It was the most beautiful train set in the world. It came complete with drivers and guards, and people waiting at stations with suitcases reading little miniature newspapers. But the train always ran in a circle. Over the bridge, through the tunnel, through the first station, across the level crossing with the cattle grid to the second station. Round and round, round and round.
Time is like that toy train.
We are passengers on a train which travels in an eternal circle. Every seven days, we go through a station called Shabbos. It's the same station. It's the same Shabbos. Similarly, every spring we revisit the train station called Pesach.