The iCalendar validator at recently celebrated its 3rd anniversery.  Active development continues with the recent release of version 1.11. This version includes several new checks, including the validator's first check against RFC 7986.

RFC 7986 was released in October 2016 as an addendum, not a replacement, for the iCalendar specification 5545. However, one of the few areas of RFC 7986 where it replaces the original specification is with the UID property. The original specification suggests the use of host names, IP addresses and domain names in the creation of the UID string. This suggestion was removed in RFC 7986 and rewritten to exclude any identifying strings due to privacy issues and instead use a random string. The validator checks for domain names simply by checking for a major TLD at the end of the UID (i.e., ".com") and generates a warning. This is not an exhaustive check but it does signal to the user to refer to the new recommendation.

Other checks have been added for the DTSTART and DTEND values. There is now a check to verify the DTEND date does not occur before the DTSTART date, and another check to verify the DTSTART and DTEND date types are the same. DTSTART and DTEND must both be either dates or date-time values and mixing of types will now generate an error.