What about a new unit of length instead?
A light-league is the distance travelled by light in 10 billionths of a day.
1 ll = 10-10 d
It is close to the ancient celtic league.
1 ll = 2.59020683712 km
A light-league is to a mile what a mile is to a kilometer.
1 ll ≈ 1.609 mi
1 mi ≈ 1.609 km
It's a pretty cool unit.