For years, we have received a calendar/diary on which we record our appointments. It is a vital source for keeping us on track with medical appointments, concerts, parties, and other engagements. Each day has its own space, and some of them list important dates. I'm not really sure why Americans want to know the date of the Japanese Emperor's birthday, but it is listed.
I recently took a look at some entries for December. I was astonished to see "Christmas observed" listed for Christmas Eve. Now, it is true that our family celebrates Christmas (in accordance with Barbara's Norwegian roots) on Christmas Eve. However, we observe Christmas on only one day: December 25. Of course, I understand that these calendars are designed for business people. When a day which is normally a holiday occurs on a Saturday or Sunday, the holiday is "observed" on an adjacent day.
I looked ahead in the new calendar. It has several entries for December 26. I read that Christmas will be observed in the United States, Canada, and Mexico. At the same time, it will be "Boxing Day" in Canada. Furthermore, Kwanza begins that day. Not surprisingly, another entry reads "all markets closed".