[Tickets #12900] Weekly by day recurring event ICS export issue with timezone

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Ticket URL: http://bugs.horde.org/ticket/12900
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  Ticket             | 12900
  Created By         | horde at gavintech.com
  Summary            | Weekly by day recurring event ICS export issue with
                     | timezone
  Queue              | Kronolith
  Version            | 4.1.4
  Type               | Bug
  State              | Unconfirmed
  Priority           | 2. Medium
  Milestone          |
  Patch              |
  Owners             |
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horde at gavintech.com (2014-01-03 04:06) wrote:

Horde exports this recurring event in ICS format:

BEGIN:VEVENT
DTSTART:20090915T013000Z
DTEND:20090915T043001Z
DTSTAMP:20140103T033921Z
UID:20090913191940.14556mns5e2c5n28@(myserver)
CREATED:20110501T223030Z
LAST-MODIFIED:20110501T223030Z
SUMMARY:(some event)
CLASS:PUBLIC
STATUS:CONFIRMED
TRANSP:OPAQUE
RRULE:FREQ=WEEKLY;INTERVAL=1;BYDAY=MO
EXDATE;TZID=America/Vancouver:20091117T023000Z
END:VEVENT

We are UTC -8 (UTC -7 during DST when the event was created) here.   
The event is Mondays at 6:30 pm, or UTC 1:30 am on Tuesday.

Since you are exporting the date in UTC format, programs I'm importing  
the event into expect the "RRULE" recur on day to be the UTC day as  
well.  So, it should be Tuesday rather than Monday for this event,  
because the event happens on Tuesday UTC rather than Monday UTC.

I have confirmed that even though Horde displays this recurring event  
on Mondays, both Thunderbird/Lightning, IOS 7, and Google Calendar  
display this event on Sundays.  They both get the time right, but the  
day is off by one.

Recurring events that happen on the same day UTC and UTC -8 appear on  
the correct day in these applications, so it's just this weird case  
where the recurring event occurs on a different day UTC vs. UTC -8  
(ie: events after 4:00 pm).