Right now I’m using google-rfc-2445 library to evaluate recurring events, and generate actual dates, for example to know when will occur event defined by following RRULE: RRULE:FREQ=MONTHLY;BYDAY=MO,TU,WE,TH,FR;BYSETPOS=-1 I’m using biweekly library to generate *.ics files. Actually it does same as iCal4j but API much more easy to use. I see that both libraries have at some level interchangeable functionality, so