There are 14 different calendars possible -- With Jan 1 on each different weekday, in both regular and leap-year form.

An interesting idea for schools (and other places) would be to put up a calendar for a year from the past which has the same form as the current year. For example, an old 1995 Calendar would work mostly fine for 2006.

One could use real calendars, or specially made calendars which would talk about the history of the year in question, showing events which took place on the days those years ago.

Certain holidays are not the same each time around, such as Easter and holidays from the Jewish calendar and other calendars. And of course some holidays are modern, like MLKing day. A modern retro-calendar could show both. (Puzzle: How many calendars are there if you factor in Easter/Passover and the major Jewish holidays?)

In 2020, it might be fun to use, for part of the year, the 1752 calendar (USA/UK) which, after Wed September 2, jumped immediately to Thursday, Sept 14. This was the gregorian calendar correction. One would have to replace the calendars on Sept 2 with some other year to keep them accurate, and tell the story.

Calendars could also be printed with historical scenes and other worthwhile lessons.

And for fun, one could do a future calendar as well, with imagined events of history.