The IETF has published the revision to iCalendar

RFC5545, Internet Calendaring and Scheduling Core Object Specification (iCalendar) has been published by the IETF as a Proposed Standard Protocol. This is the revision to RFC 2445 (iCalendar) which has been underway for some time. RFC5545 obsoletes RFC2445. See http://www.rfc-editor.org/rfc/rfc5545.txt. CalConnect congratulates everyone who was involved in progressing this work.