What time is good to leave from Virginia to Connecticut to avoid Traffic?

What time is good to leave from DC to Connecticut to avoid Traffic in all the states in between? I'm renting a car and making a round trip, doing this in the shortest amount of time possible would be best, so I definitely need to avoid traffic. I'm thinking leave some time around 7PM at night, then by the time I get up to the DC area it will be about 9PM, and just cruise up to Shelton, CT and get back before 7AM the next day and avoid the traffic.