Some people seem to be under the mistaken impression that the recess appointment of Donald Berwick will expire at the beginning of 2011, once the new Congress is sworn in, but he’ll actually be able to maintain his post as head of the Centers for Medicare and Medicaid Services until late 2011.

As Article II, Section 2, of the U.S. Constitution reads:

The President shall have power to fill up all vacancies that may happen during the recess of the Senate, by granting commissions which shall expire at the end of their next session.

Each two-year Congress is divided into two sessions, meaning that Berwick’s appointment will be good until the end of next year’s session, or about a year and a half from now.