It's what an NBC Nightly News anchor said when starting another news story:
My question is whether she could have said on a Christmas Eve instead. I would think that on Christmas Eve indicates that the context is confined to the current year, whereas on a Christmas Eve that it is extended over two or more years. And the context of the quoted portion seems to encompass more than a hundred years.Another big story on this night. A historic vote, a first for the Senate on Christmas Eve since the late 1800s, bringing health care reform one step closer to reality. Senate Democrats pushed through their version of the bill against unanimous opposition from Republicans.