Burning the midnight oil is about to pay off for millions of U.S. millennials.

The White House on Tuesday announced a new rule that will boost the number of Americans who qualify for time-and-a-half pay whenever they work more than 40 hours in a given week. Among the biggest beneficiaries may be overworked young employees, toiling at startups and ad agencies or serving as restaurant managers, who so far haven't been getting the extra compensation for working around the clock.

The new rule, which takes effect on December 1, doubles the salary threshold for overtime eligibility to $47,476 a year from the current $23,660. That means that employees earning an annual salary at the new threshold or lower will automatically be eligible for overtime wages, just like hourly workers who already qualify for this extra rate.