When A Child Is Born takes place on Christmas (though it is not that child that is born). Max and her team end up being sidetracked while they are hiking towards William I's coronation. It's short and sweet and it fits perfectly in the holiday season.
While I enjoyed it thoroughly, all 20 or so pages of it, it did seem a bit incongruent with the previously established laws of the series. (This is something that slightly bothered me throughout the whole series, but here it is very clear). It seems to me there is a regular switch in exactly how much they can interfere with history.
Nevertheless, a sure recommendation to the fans of the series!