just started using them recently for a rails project I've been working on. I cannot recommend this project enough, saved me hundreds of hours.
if you want a crash course in implementing it in a rails app, look no further then these 2 AWESOME drifting ruby episodes:
https://www.driftingruby.com/episodes/fullcalendar-events-an...
https://www.driftingruby.com/episodes/recurring-events-with-...