[Saxon]

To understand the 7th day thing, try replaying the moves when you get your simultaneous move back. They are the pink buttons up in the right hand corner that look like a VCR (at least I think they are, I only did this once). What you will see is that the ships move one day at a time and there are a number (30?) of days in each turn. What this means for the intercept attack is that each ship moves, if it has the available movement on said day, then checks it’s orders. If it’s target has moved, it changes it’s goal and moves that way on the next day it has a move.

I figure the 7th day means that the ships have to be together on the 7th, 14th, 21st and 28th of the month. If you have a faster ship, it gives you a chance to escape the battle, as that slower ship has to keep up with you until one of the 7th days.

Anyway, that is just my take on it. Try replaying some turns and you might find out more.