New package to add recurring events to the diary and calendar

I made a little package to add recurrent dates with odd rules to the diary -- things like "do this on the last working day of the month" taking holidays into account. They are intended for the diary and the calendar, though you can make them show up on the org-mode agenda. I did a quick write up here for anyone interested: [https://mrincon.net/posts/org-calendar/](https://mrincon.net/posts/org-calendar/) The package is here: [https://github.com/foxfriday/date-functions](https://github.com/foxfriday/date-functions) The package is not refined, and I suspect the uses are pretty limited, but perhaps someone other than me will find it useful. If so I'll try to add more documentation and non U.S. holidays. I was encouraged by the surprising discovery that a few people found the ink.el package useful (thanks).

Trying to work out whether this addresses the problems I've had with Org's scheduling limitations. First thing I notice is that your package's identifiers don't include a package-specific prefix. They look like they come from a package called `diary`.

I added identifiers for the two main functions. I should have done that from the start. That still leaves the variables "date" and "entry". Those variables get dynamically bound by the `dairy` package when the `sexp entries` are loaded. All that occurs behind the scenes. If you want to see the entries in your org-mode agenda, all you have to do is set `(setq org-agenda-include-diary t)`. Just keep in mind that those entries will look like holidays, so as far I know you cannot have TODOs or anything like that on them. The Emacs diary and calendar are much more spartan than the org-agenda. For those interested in the Emacs diary here is an excellent video about it by the always excellent Protesilaos: https://protesilaos.com/codelog/2021-04-14-emacs-diary-calendar