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You have to run the commands making the calendar directory and file first.

Here on 10.4 :-) Man page: "A calendar command appeared in Version 7 AT&T UNIX." Last line says "BSD June 13, 2002."

Strange. I'm on 10.12 too, but I have it.

It's present on 10.12.6 here, and also 10.6.8, so it doesn't seem to be new.

I have it on High Sierra (10.13)