Subject: [calsify] [Errata Verified] RFC5545 (4271)

From: RFC Errata System <[email-masked]>
Date: Tue, 17 Feb 2015 13:19:04 -0800 (PST)

The following errata report has been verified for RFC5545,
"Internet Calendaring and Scheduling Core Object Specification (iCalendar)". 

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You may review the report below and at:
http://www.rfc-editor.org/errata_search.php?rfc=5545&eid=4271

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Status: Verified
Type: Technical

Reported by: Neil Jenkins <[email-masked]>
Date Reported: 2015-02-12
Verified by: Barry Leiba (IESG)

Section: 3.3.10

Original Text
-------------
Recurrence rules may generate recurrence instances with an invalid
date (e.g., February 30) or nonexistent local time (e.g., 1:30 AM
on a day where the local time is moved forward by an hour at 1:00
AM).  Such recurrence instances MUST be ignored and MUST NOT be
counted as part of the recurrence set.

Corrected Text
--------------
Recurrence rules may generate recurrence instances with an invalid
date (e.g., February 30). Such recurrence instances MUST be ignored
and MUST NOT be counted as part of the recurrence set.

Recurrence rules may generate recurrence instances with a nonexistent
local time ((e.g., 1:30 AM on a day where the local time is moved
forward by an hour at 1:00 AM).  Such recurrence instances are
handled as specified in Section 3.3.5.

Notes
-----
The section about ignoring times that don't occur in the timezone of the expansion is contradicted by the later passage (p44):

"""If the computed local start time of a recurrence instance does not
exist, or occurs more than once, for the specified time zone, the
time of the recurrence instance is interpreted in the same manner
as an explicit DATE-TIME value describing that date and time, as
specified in Section 3.3.5."""

And this is the behaviour implemented by major clients such as Calendar.app and Google Calendar.

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RFC5545 (draft-ietf-calsify-rfc2445bis-10)
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Title               : Internet Calendaring and Scheduling Core Object Specification (iCalendar)
Publication Date    : September 2009
Author(s)           : B. Desruisseaux, Ed.
Category            : PROPOSED STANDARD
Source              : Calendaring and Scheduling Standards Simplification
Area                : Applications
Stream              : IETF
Verifying Party     : IESG