So, this is actually a specific request for advice and information relevant to my game, but I figure it might spur a more general discussion around the topic as well.
I'm currently running a TSOY game based on an old D&D campaign. Right now, one PC is trying to sail from one island to another in a small, perhaps 30 or 50-oar galley (a triaconter or penteconter; this is an ancient Mediterranean-flavored setting). This evening I found myself figuring out how many nautical miles it was from one island to the next, and vainly searching the internet for information on the average knots per day of ancient vessels, in order to figure out how many days it would take the PC to complete his journey. I was unable to figure this out. Obviously there are no seafaring rules for TSOY. The question is, am I getting too old-school D&D with this? How can I handle overland and overseas travel in my game without getting bogged down in minutiae, while still making things like... one PC having a particularly fast ship (represented by multiple Secrets) meaningful?
Are there any games or game books that include this kind of information, or good systems for this kind of travel?
More broadly, how do you handle long-distance travel in your fantasy games?