Sunrise and Sunset times

[Targan]

It is very useful. On a related note, I've mentioned in other threads that knowing the date and location you're at, and having some sort of almanac with sunrise and sunset times, would allow you to make accurate corrections to timekeeping devices which in turn is invaluable for navigation where dead reckoning is not possible (such as navigating at sea). Of course, the resetting of timepieces would have to be done while you're still at a known location, not at sea.