https://app.knowbase.one/vault/rfc/docid/8180
RFC7529: Non-Gregorian Recurrence Rules in the Internet Calendaring and Scheduling Core Object Specification (iCalendar)
Internet Engineering Task Force (IETF) C. Daboo Request for Comments: 7529 Apple Inc. Updates: 5545, 6321, 7265 G. Yakushev Category: Standards Track Google Inc. IS...