RFC 5545, "Internet Calendaring and Scheduling Core Object Specification (iCalendar)", September 2009

Note: This RFC has been updated by RFC 5546, RFC 6868, RFC 7529, RFC 7953, RFC 7986, RFC 9073, RFC 9074, RFC 9253

Errata ID: 6316
Status: Reported
Type: Technical
Publication Format(s) : TEXT
Reported By: Ken Murchison
Date Reported: 2020-10-22

Section 3.8.5.1 says:

    Value Type:  The default value type for this property is DATE-TIME.
       The value type can be set to DATE.

It should say:

    Value Type:  The default value type for this property is DATE-TIME.
       The value type can be set to DATE.  This property MUST have the same
       value type as the "DTSTART" property contained within the
       recurring component.  Furthermore, this property MUST be specified
       as a date with local time if and only if the "DTSTART" property
       contained within the recurring component is specified as a date
       with local time.

Notes:

EXDATE excludes a specific instance of a recurring event and therefore should have the same value type as DTSTART. This is analogous to RECURRENCE-ID which overrides a specific instance and has the same value type as DTSTART.

I will note however that there is iCalendar data in the wild with DTSTART;VALUE=DATE-TIME and EXDATE;VALUE=DATE. If this errata is rejected as incorrect, then a new errata should be opened with additional text describing how EXDATE;VALUE=DATE is supposed to be handled when DTSTART;VALUE=DATE-TIME. For instance, does EXDATE;VALUE=DATE exclude ALL instances of a FREQ=HOURLY recurrence on the given day?

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