Dang, that IS a good question. But, without the option to take sun sights and shoot stars with a sextant, I'm not certain exactly how knowing the time zone would HELP, but it is a valid question.
There is a game called Virtual Skipper that lets you try celestial navigation, among many other things, but that is not implemented here. I do think that should be an option, however. I believe that would be harder to learn how to do than manual torpedo aiming.
At any rate, I do wish there was a graphics option for more stars and the Milky Way, but I am getting off topic...
It is based on your home port time. Whatever your home port is that is what the clock is set to. I know, it scrambles my sensibilities too but that is how they designed it. The map is FLAT not spherical so distance north or south of the equator will not change the sunrise/set times.
Well as long as we know the timezone we can figure the longitude pos from sunrise or sunset. The Latitude we can get from sighting/fixing polaris with a custum made Sextant. (mine is a printed scale on a transparent paper)
OR we can use "Big Circles" with three star fix's to make an astronomical position from witch we can make an estimated position that would be ok.
BUT in order for both to work we NEED the devs to explain what they did with the time. What zone is "Base Time" does it change with dateline or travel or with summer time??