We set up a recurring event in Team Calendar. I have subscribed the calendar in Outlook. Since a few weeks, I get the attached error message (in German language) which says:
There is a VEVENT in the subscribed calendar with the timezone setting TZID value "Europe/Berlin" which is not declared.

I tried to analyse this and exported and downloaded the ics file directly from our Team Calendar. Here are the most relevant lines:

BEGIN:VCALENDAR
PRODID:-//Atlassian Confluence//Calendar Plugin 1.0//EN
VERSION:2.0
CALSCALE:GREGORIAN
X-WR-CALNAME:exensio
X-WR-CALDESC:
X-WR-TIMEZONE:Europe/Berlin
X-MIGRATED-FOR-USER-KEY:true
METHOD:PUBLISH
BEGIN:VTIMEZONE
SEQUENCE:12244
BEGIN:DAYLIGHT
TZOFFSETFROM:+0100
TZOFFSETTO:+0200
TZNAME:CEST
DTSTART:19810329T020000
RRULE:FREQ=YEARLY;BYMONTH=3;BYDAY=-1SU
END:DAYLIGHT
BEGIN:STANDARD
TZOFFSETFROM:+0200
TZOFFSETTO:+0100
TZNAME:CET
DTSTART:19961027T030000
RRULE:FREQ=YEARLY;BYMONTH=10;BYDAY=-1SU
END:STANDARD
BEGIN:STANDARD
TZOFFSETFROM:+005328
TZOFFSETTO:+0100
TZNAME:CET
DTSTART:18930401T000000
RDATE:18930401T000000
END:STANDARD
BEGIN:DAYLIGHT
TZOFFSETFROM:+0100
TZOFFSETTO:+0200
TZNAME:CEST
DTSTART:19160430T230000
RDATE:19160430T230000
RDATE:19170416T020000
RDATE:19180415T020000
RDATE:19400401T020000
RDATE:19430329T020000
RDATE:19440403T020000
RDATE:19450402T020000
RDATE:19460414T020000
RDATE:19470406T030000
RDATE:19480418T020000
RDATE:19490410T020000
RDATE:19800406T020000
END:DAYLIGHT
BEGIN:STANDARD
TZOFFSETFROM:+0200
TZOFFSETTO:+0100
TZNAME:CET
DTSTART:19161001T010000
RDATE:19161001T010000
RDATE:19170917T030000
RDATE:19180916T030000
RDATE:19421102T030000
RDATE:19431004T030000
RDATE:19441002T030000
RDATE:19451118T030000
RDATE:19461007T030000
RDATE:19471005T030000
RDATE:19481003T030000
RDATE:19491002T030000
RDATE:19800928T030000
RDATE:19810927T030000
RDATE:19820926T030000
RDATE:19830925T030000
RDATE:19840930T030000
RDATE:19850929T030000
RDATE:19860928T030000
RDATE:19870927T030000
RDATE:19880925T030000
RDATE:19890924T030000
RDATE:19900930T030000
RDATE:19910929T030000
RDATE:19920927T030000
RDATE:19930926T030000
RDATE:19940925T030000
RDATE:19950924T030000
END:STANDARD
BEGIN:DAYLIGHT
TZOFFSETFROM:+0200
TZOFFSETTO:+0300
TZNAME:CEMT
DTSTART:19450524T020000
RDATE:19450524T020000
RDATE:19470511T030000
END:DAYLIGHT
BEGIN:DAYLIGHT
TZOFFSETFROM:+0300
TZOFFSETTO:+0200
TZNAME:CEST
DTSTART:19450924T030000
RDATE:19450924T030000
RDATE:19470629T030000
END:DAYLIGHT
BEGIN:STANDARD
TZOFFSETFROM:+0100
TZOFFSETTO:+0100
TZNAME:CET
DTSTART:19460101T000000
RDATE:19460101T000000
RDATE:19800101T000000
END:STANDARD
END:VTIMEZONE

BEGIN:VEVENT
DTSTAMP:20150921T070409Z
SUMMARY:Standup-Meeting
UID:20150423T085725Z--583630932@cm.exensio.com
DESCRIPTION:Besprechung
ORGANIZER;X-CONFLUENCE-USER-KEY=ed6fbc8b4acb72d9014acdf711870001;CN=my colleague;CUTYPE=INDIVIDUAL:xxx@exensio.de
RRULE:FREQ=WEEKLY;WKST=SU;INTERVAL=1
CREATED:20150423T085725Z
LAST-MODIFIED:20150423T085725Z
SEQUENCE:1
X-CONFLUENCE-SUBCALENDAR-TYPE:other
TRANSP:TRANSPARENT
STATUS:CONFIRMED
DTSTART:20150424T110000Z
DTEND:20150424T111500Z
END:VEVENT

BEGIN:VEVENT
DTSTAMP:20150921T070409Z
SUMMARY:Standup-Meeting
UID:20150423T085725Z--583630932@cm.exensio.com
DESCRIPTION:Besprechung
ORGANIZER;X-CONFLUENCE-USER-KEY=ed6fbc8b4acb72d9014acdf711870001;CN=my colleague;CUTYPE=INDIVIDUAL:xxx@exensio.de
RECURRENCE-ID;TZID=Europe/Berlin:20150424T130000
CREATED:20150423T085747Z
LAST-MODIFIED:20150423T085759Z
SEQUENCE:2
X-CONFLUENCE-SUBCALENDAR-TYPE:other
TRANSP:TRANSPARENT
STATUS:CONFIRMED
DTSTART:20150424T110000Z
DTEND:20150424T111500Z
END:VEVENT