An 1872 law established the first Tuesday after the first Monday in November as Election Day. An ordinary act of Congress could designate Election Day as a national holiday, thereby giving more people more time to vote. As noted before, this would probably be resisted on the basis of cost. A solution would be to move Election Day to the second Tuesday of November and combine it with Veterans' Day, traditionally celebrated on November 11.
In an era where voter turnout continues to decline, especially during the mid-term election cycle, this would be just one strategy to emphasize the importance of voter participation in the democratic process.