Sarah and Mike conclude that it is wednesday. But five minutes later it is already friday. How is that possible?

Sarah and Mike are on wednesday around 23.58h on a boat just east of the date line. That imaginary line goes across the middle of the pacific ocean. They sail in western direction and pass the date line. So it becomes thursday. But because 5 minutes later it is already over 24.00h, it becomes another day later. So suddenly it is already friday.

Remark: a big part of the date line goes through the same time zone. So if you then pass the date line, the time does not change. In a small part the clock will be put back by 1 or 3 hours (in the neighborhood of Alaska). If Sarah and Mike are in such a place, they have to wait some additonal hours before it becomes friday.