Ok this has nothing to do with cruises really, but for interest sake. When I was in the engine room in the Navy, we took hourly logs. Any underways we had we never changed time if we were going back to the same port. However, if we ended up in a different port, we would just change the time zones all at once the night before. Our logs looked really wacky when we crossed the international date line, but it was still easier than adjusting every time we crossed a time zone. Keep in mind, we were often at sea for weeks/months at a time (submarines) and didn't see the sun rise or fall, so jumping ahead or back a number of hours was more a matter of paperwork than anything else.