ICS files from Microsoft Outlook differ from those that were created by Gnome Evolution. (semicolons are used instead of colons at some position) Evolution --------- all line endings are \r\n all day event: DTSTART;VALUE=DATE:20230908 DTEND;VALUE=DATE:20230909 an all day event can span over multiple days and look like this: DTSTART;VALUE=DATE:20230911^M$ DTEND;VALUE=DATE:20230916^M$ appointment: DTSTART;TZID=/freeassociation.sourceforge.net/Continent/City: 20230909T090000 DTEND;TZID=/freeassociation.sourceforge.net/Continent/City: 20230909T093000 appointments can also span over multiple days: DTSTART;TZID=/freeassociation.sourceforge.net/Europe/Berlin: 20230913T230000 DTEND;TZID=/freeassociation.sourceforge.net/Europe/Berlin: 20230914T040000 SEQUENCE is the number of times the event was modified. Evolution sets this to 2 after it has been generated. Appointments include the continent and city of the used time zone. "DESCRIPTION:" is an optional field.