A commercial airliner takes about 7 hours to Paris and 8 to Milan. You can add an hour for the flight back. A learjet should be about the same, give or take half an hour.
Paris is six hours ahead of the East Coast, so if they want to eat dinner at 8pm, they would have to leave 6am, local time in the US, (adding a comfortable hour for travel from the airport to the restaurant.)
Oh, and you should add an extra hour on the trip back because the wind is slowing the plane down on the trip West.
Michael
