Updating an Event with another .ics-File

Question

I am trying to update an event in Microsoft Outlook 2016. I have 2 .ics-files. The second one is supposed to overwrite and update the first one if they have the same UID, but I am still getting two separate Events in my calendar after implementing. I am using the net.fortuna.ical4j library for generating those files. Here are my two files:

BEGIN:VCALENDAR
PRODID:-//myProdId
VERSION:2.0
CALSCALE:GREGORIAN
BEGIN:VEVENT
DTSTAMP:20201126T105020Z
DTSTART;VALUE=DATE:20201126
SUMMARY:Ay
UID:20201126T105020Z-uidGen@fe80:0:0:0:dd32:894f:88da:fde6%wlan0
SEQUENCE:1
DESCRIPTION:
ORGANIZER:supervisor
END:VEVENT
END:VCALENDAR

And the second file to overwrite the first event:

BEGIN:VCALENDAR
PRODID:-//myProdId
VERSION:2.0
CALSCALE:GREGORIAN
BEGIN:VEVENT
DTSTAMP:20201126T105043Z
DTSTART;VALUE=DATE:20201127
SUMMARY:Ay
UID:20201126T105020Z-uidGen@fe80:0:0:0:dd32:894f:88da:fde6%wlan0
SEQUENCE:2
DESCRIPTION:
ORGANIZER:supervisor
END:VEVENT
END:VCALENDAR

What is causing the problem here?

Answer 1

Outlook may also check for modification by checking LAST-MODIFIED too See: https://www.rfc-editor.org/rfc/rfc5545#section-3.8.7.3