Some events from accepted invitations are displayed with the wrong time

[logological]

In Issue #342 I reported a problem where, if I created a new event in Thunderbird in my system timezone (America/Winnipeg), then after saving that event, the event timezone changes to America/Chicago and Thunderbird displays it starting and ending an hour later than I originally specified. That problem was fixed for the case where I create a new event myself, but I am still seeing it with some events that others invite me to.

For example, a couple days ago I received an e-mail invitation for a half-hour meeting starting at 13:00. An excerpt from the calendar file is as follows:

BEGIN:VCALENDAR
METHOD:REQUEST
PRODID:Microsoft Exchange Server 2010
VERSION:2.0
BEGIN:VTIMEZONE
TZID:Central Standard Time
BEGIN:STANDARD
DTSTART:16010101T020000
TZOFFSETFROM:-0500
TZOFFSETTO:-0600
RRULE:FREQ=YEARLY;INTERVAL=1;BYDAY=1SU;BYMONTH=11
END:STANDARD
BEGIN:DAYLIGHT
DTSTART:16010101T020000
TZOFFSETFROM:-0600
TZOFFSETTO:-0500
RRULE:FREQ=YEARLY;INTERVAL=1;BYDAY=2SU;BYMONTH=3
END:DAYLIGHT
END:VTIMEZONE
BEGIN:VEVENT
ORGANIZER;CN=Jordan Bass:mailto:[email protected]
ATTENDEE;ROLE=REQ-PARTICIPANT;PARTSTAT=NEEDS-ACTION;RSVP=TRUE;CN=REDACTED
DESCRIPTION;LANGUAGE=en-CA:REDACTED
UID:040000008200E00074C5B7101A82E0080000000037D1CD0ADDB1DA01000000000000000
 0100000004ABACBF9E1E8E048A49157F1874D9D33
SUMMARY;LANGUAGE=en-CA:REDACTED
DTSTART;TZID=Central Standard Time:20240530T130000
DTEND;TZID=Central Standard Time:20240530T133000
CLASS:PUBLIC
PRIORITY:5
DTSTAMP:20240529T152953Z

Before I accept this invitation, the message preview pane in Thunderbird shows the meeting time as "Thursday, 30 May 2024 13:00 – 13:30". After I accept it, Thunderbird shows the meeting time in the message preview pane as "Thursday, 30 May 2024 14:00 – 14:30" on one line, and then "Thursday, 30 May 2024 13:00 – 13:30" crossed out on the second line. And then in Thunderbird's today pane or in the calendar tab, the meeting is shown as taking place from 14:00 to 14:30. However, if I double-click on the calendar entry, the "Edit Event" dialog shows the meeting time as 13:00 to 13:30 (in America/Chicago)! There seems to be no consistency whatsoever…

Not every accepted event gets mangled in this way, but I haven't managed to determine which events get their time changed and which don't.