I hate to be that guy, but why not use pscal ?

It has all you want, plus moon phases!

It's admittedly harder to find these days, and someone should rewrite it in a decent language, but here it is:

https://www.panix.com/~mbh/pscal/

And I also hate to be that guy but pscal...

> someone should rewrite it in a decent language

was coded in BAGS (bash, awk, grep, sed) and Postscript circa 1987 [1], and it's still working almost 40 years later in 2026 !

Perhaps it was in fact coded decently. And licensed decently as well. ^_^

[1]

    AUTHOR:
        Patrick Wood
        Copyright (C) 1987 by Pipeline Associates, Inc.
        Permission is granted to modify and distribute this free of charge.