On a route from A to B which is around 600nM the time by boat a a speed of 6 knts is 96 hours (4 days and 4 hrs). At a speed of 5.6 is 4 days and 12 hrs, but at a speed of 5.4 knts it is 4 days and 9 hrs - faster than at 5.6 knts. ???

At 5 knts it should be 120 hors (exactly 5 days) but it shows 5 days and 3 hours.
So monething is fishy here :-)

Beside this bug, your program is amazing. thank your very much for your great work