OK the work went on more quickly than expected.
Much of the classes are created and the things are starting to work.
Will have to fix all the date math operations (addition of instants etc) and week behaviour.
I decided to use the "degenerated month" approach so that some month have just 1 (or 2 in the case of Shieldmeet leap year)days this create a mess with the week calculation since also "Degenerated weeks" come out.
All this complicate math a bit.
The lib is really well done, even if quite complex.
There a really wanderful decoupling implementation so that adding a chronology has been easy and did not request adding a single line of code to base classes.
Would see more of these projects around.