Hello,
RSCALE=CHINESE
RSCALE=ETHIOPIC
RSCALE=HEBREW
RSCALE=GREGORIAN
…
These are part of RFC 7529 (iCalendar Extensions for Non‑Gregorian Recurrence Rules), perhaps not supported inside iCalendar?
RFC7529.zip (1.7…... While both RFCs are valid iCalendar extensions, their...focused on interoperable calendar data exchange, implementing features...