James L. Brooks, the writer of this episode, wrote a sequel (of sorts) for a different character and series: Christmas and the Hard-Luck Kid II (1970), that sitcom's first Christmas special.
This story takes place during Christmas 1963, since the air date is 1966 and the story flashes back three years to Ann's earlier job in a boarding school. (The fashions, however, are definitely more 1966 than 1963.)
Christopher Shea, the child-actor playing Tommy, is best known as the voice of Linus in A Charlie Brown Christmas (1965), It's the Great Pumpkin, Charlie Brown (1966), and several other Peanuts specials. At the time this episode was broadcast, Shea was also a regular cast member in the short-lived Western series Shane (1966).
This story takes place in December 1963, three years prior to the present (1966).
Filming took place on or about November 11, 1966.