Issues found by KolabNow customer (OTRS#1014526).
1. It seems that event records in ics file don't have valid UID (all UIDs are empty). E.g.Thunderbird/Lightning will not import such events.
2. All records in ics file are set to year 2025 for some reason. This is not nice, however I'm not sure how we can improve that. Use current year or 365 days starting from current date? Or maybe we could make these events recurrent?
Here's an example of event record:
BEGIN:VEVENT
UID:
DTSTAMP;VALUE=DATE-TIME:20151123T204804Z
DTSTART;VALUE=DATE:20250408
DTEND;VALUE=DATE:20250409
SUMMARY:Barto's Birthday
DESCRIPTION:Age 40
BEGIN:VALARM
ACTION:DISPLAY
TRIGGER:-P1D
END:VALARM
END:VEVENT