The busiest travel day of the year is December 1st because it's near the Holidays.
Other than December 1st other days that are the Holidays are the busiest days to travel and more people are on the road traveling to relatives houses for Christmas, Thanksgiving, Easter etc.
The day after the Holidays are also busy travel days because some people leave out the next day after the Holiday but some may stay a bit longer.
If you want to travel out of state to a relatives house for a Holiday then it's best to leave a few days before the Holidays to get there.
That way you don't have to get into a bunch of traffic especially in cities and larger towns.