This is actually what prompted me to start work on luatz: https://github.com/daurnimator/luatz https://github.com/daurnimator/luatz Trying to implement RRULEs

This is actually what prompted me to start work on luatz: https://github.com/daurnimator/luatz https://github.com/daurnimator/luatz Trying to implement RRULEs you need all sorts of fun date math + converting back and forth between time zones. I never released my ical library (didn't get it open sourced from work); but luatz lets you write your own :)