Tickets :: Comment on [#4399] Broken iCalendar event timezone interoperabilty with Outlook & others

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Comment	> Attached is a patch (against HEAD - 1 Sep 2006) that adds proper > timezone handling to the Horde framework so that icalendar > invitations / events sent from users in other timezones are viewed > and imported properly. > > > > I did this patch the right way and the code conforms to the iCalendar > specification (RFC2445). I have extensively tested it and I am > satisfied that it interoperates correctly with all RFC conforming > calendar applications including Microsoft Outlook / Exchange, Apple > iCal, Mozilla Calendar and others. Further, the changes are all in > one file and internal to the iCalendar object in the Horde framework > so there are no changes that are necessary to the applications > (Kronolith, IMP, etc.) Therefore, I believe this patch is ready for > immediate integration into Horde CVS. The only externally visible > change made (besides correct date / times!) is what gets stored in > the calendar object when an invalid date-time stamp is encountered. > Previously, it was not consistent but usually false would be stored. > After this patch the original text from the invitation is stored so > that it's not lost. > > > > After applying this patch you will need to run > > > > framework/install-packages.php -p iCalendar > > > > from the command line as root for it to take affect. > > > > One final caveat: because of the way the standard works the sending > application specifies the exact times of the timezone's changes > between daylight and standard time (if any). This means that if the > powers that be change the dates for those changes and the sending > application does not know about the new rules at the time the > invitation is sent then there is potential for the receiving > application (including this code) calculating the incorrect time. > That is not a bug in the code but an invitation with a timezone > component specified that is not correct. The sender will need to send > an updated invitation after updating his computer / software to know > about the new timezone rules or the recipient will need to manually > change the time of the event. > > > > I bring this up of course because the US congress has changed when we > in the US observe our time changes starting in 2007. If the sending > application / computer of an invite does not know that and it encodes > incorrect old information about its timezone but the recipient's > application / computer knows about the new changes and the invitation > falls on a date between when the sending application thought the time > change would occur and when the receiving application knows that it > actually will occur then the time derrived from the invitation will > be off. Is that confusing enough? > > > > To put it simply, if you notice that some invitations sent by people > in US timezones for events between March 11, 2007 and April 1, 2007 > appear to be showing up witch a time that is incorrect by exactly one > hour, it's not a bug in my code but a problem at the sender's end! > Any software that imports calendar events using the standard may have > this problem. > > > > Thank you, > > Carl E. Thompson
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