This is a library for arbitrary dates.
Most programming languages have pretty good support for the Gregorian calendar. That doesn't help me much when I'm trying to write a book that doesn't use the Gregorian calendar.
This will eventually be rolled in to the rest of my book-writing software.
If you're doing any programming where you need to handle non-gregorian dates, this library may well work for you.
WARNING: Doesn't respect relativity. Sci-fi may not work here.